reducing scope of loop counters, and micro-optimising loops by using != where safe and pre-increment wherever return value is not used

1 files changed, 184 insertions, 192 deletions

diff --git a/lodepng.cpp b/lodepng.cpp
index 31f146d..fd61675 100644
--- a/lodepng.cpp
+++ b/lodepng.cpp
@@ -174,7 +174,7 @@ static unsigned uivector_resizev(uivector* p, size_t size, unsigned value)
 {
   size_t oldsize = p->size, i;
   if(!uivector_resize(p, size)) return 0;
-  for(i = oldsize; i < size; i++) p->data[i] = value;
+  for(i = oldsize; i < size; ++i) p->data[i] = value;
   return 1;
 }
 
@@ -198,7 +198,7 @@ static unsigned uivector_copy(uivector* p, const uivector* q)
 {
   size_t i;
   if(!uivector_resize(p, q->size)) return 0;
-  for(i = 0; i < q->size; i++) p->data[i] = q->data[i];
+  for(i = 0; i != q->size; ++i) p->data[i] = q->data[i];
   return 1;
 }
 #endif /*LODEPNG_COMPILE_ENCODER*/
@@ -260,7 +260,7 @@ static unsigned ucvector_resizev(ucvector* p, size_t size, unsigned char value)
 {
   size_t oldsize = p->size, i;
   if(!ucvector_resize(p, size)) return 0;
-  for(i = oldsize; i < size; i++) p->data[i] = value;
+  for(i = oldsize; i < size; ++i) p->data[i] = value;
   return 1;
 }
 #endif /*LODEPNG_COMPILE_DECODER*/
@@ -319,10 +319,10 @@ static void string_cleanup(char** out)
 
 static void string_set(char** out, const char* in)
 {
-  size_t insize = strlen(in), i = 0;
+  size_t insize = strlen(in);
   if(string_resize(out, insize))
   {
-    for(i = 0; i < insize; i++)
+    for(int i = 0; i != insize; ++i)
     {
       (*out)[i] = in[i];
     }
@@ -418,19 +418,19 @@ unsigned lodepng_save_file(const unsigned char* buffer, size_t buffersize, const
   if(((*bitpointer) & 7) == 0) ucvector_push_back(bitstream, (unsigned char)0);\
   /*earlier bit of huffman code is in a lesser significant bit of an earlier byte*/\
   (bitstream->data[bitstream->size - 1]) |= (bit << ((*bitpointer) & 0x7));\
-  (*bitpointer)++;\
+  ++(*bitpointer);\
 }
 
 static void addBitsToStream(size_t* bitpointer, ucvector* bitstream, unsigned value, size_t nbits)
 {
   size_t i;
-  for(i = 0; i < nbits; i++) addBitToStream(bitpointer, bitstream, (unsigned char)((value >> i) & 1));
+  for(i = 0; i != nbits; ++i) addBitToStream(bitpointer, bitstream, (unsigned char)((value >> i) & 1));
 }
 
 static void addBitsToStreamReversed(size_t* bitpointer, ucvector* bitstream, unsigned value, size_t nbits)
 {
   size_t i;
-  for(i = 0; i < nbits; i++) addBitToStream(bitpointer, bitstream, (unsigned char)((value >> (nbits - 1 - i)) & 1));
+  for(i = 0; i != nbits; ++i) addBitToStream(bitpointer, bitstream, (unsigned char)((value >> (nbits - 1 - i)) & 1));
 }
 #endif /*LODEPNG_COMPILE_ENCODER*/
 
@@ -441,17 +441,17 @@ static void addBitsToStreamReversed(size_t* bitpointer, ucvector* bitstream, uns
 static unsigned char readBitFromStream(size_t* bitpointer, const unsigned char* bitstream)
 {
   unsigned char result = (unsigned char)(READBIT(*bitpointer, bitstream));
-  (*bitpointer)++;
+  ++(*bitpointer);
   return result;
 }
 
 static unsigned readBitsFromStream(size_t* bitpointer, const unsigned char* bitstream, size_t nbits)
 {
   unsigned result = 0, i;
-  for(i = 0; i < nbits; i++)
+  for(i = 0; i != nbits; ++i)
   {
     result += ((unsigned)READBIT(*bitpointer, bitstream)) << i;
-    (*bitpointer)++;
+    ++(*bitpointer);
   }
   return result;
 }
@@ -514,7 +514,7 @@ typedef struct HuffmanTree
 static void HuffmanTree_draw(HuffmanTree* tree)
 {
   std::cout << "tree. length: " << tree->numcodes << " maxbitlen: " << tree->maxbitlen << std::endl;
-  for(size_t i = 0; i < tree->tree1d.size; i++)
+  for(size_t i = 0; i != tree->tree1d.size; ++i)
   {
     if(tree->lengths.data[i])
       std::cout << i << " " << tree->tree1d.data[i] << " " << tree->lengths.data[i] << std::endl;
@@ -556,14 +556,14 @@ static unsigned HuffmanTree_make2DTree(HuffmanTree* tree)
   There is only memory for such good tree currently, if there are more nodes
   (due to too long length codes), error 55 will happen
   */
-  for(n = 0; n < tree->numcodes * 2; n++)
+  for(n = 0; n < tree->numcodes * 2; ++n)
   {
     tree->tree2d[n] = 32767; /*32767 here means the tree2d isn't filled there yet*/
   }
 
-  for(n = 0; n < tree->numcodes; n++) /*the codes*/
+  for(n = 0; n < tree->numcodes; ++n) /*the codes*/
   {
-    for(i = 0; i < tree->lengths[n]; i++) /*the bits for this code*/
+    for(i = 0; i != tree->lengths[n]; ++i) /*the bits for this code*/
     {
       unsigned char bit = (unsigned char)((tree->tree1d[n] >> (tree->lengths[n] - i - 1)) & 1);
       if(treepos > tree->numcodes - 2) return 55; /*oversubscribed, see comment in lodepng_error_text*/
@@ -578,7 +578,7 @@ static unsigned HuffmanTree_make2DTree(HuffmanTree* tree)
         {
           /*put address of the next step in here, first that address has to be found of course
           (it's just nodefilled + 1)...*/
-          nodefilled++;
+          ++nodefilled;
           /*addresses encoded with numcodes added to it*/
           tree->tree2d[2 * treepos + bit] = nodefilled + tree->numcodes;
           treepos = nodefilled;
@@ -588,7 +588,7 @@ static unsigned HuffmanTree_make2DTree(HuffmanTree* tree)
     }
   }
 
-  for(n = 0; n < tree->numcodes * 2; n++)
+  for(n = 0; n < tree->numcodes * 2; ++n)
   {
     if(tree->tree2d[n] == 32767) tree->tree2d[n] = 0; /*remove possible remaining 32767's*/
   }
@@ -605,7 +605,7 @@ static unsigned HuffmanTree_makeFromLengths2(HuffmanTree* tree)
 {
   uivector blcount;
   uivector nextcode;
-  unsigned bits, n, error = 0;
+  unsigned error = 0;
 
   uivector_init(&blcount);
   uivector_init(&nextcode);
@@ -620,16 +620,16 @@ static unsigned HuffmanTree_makeFromLengths2(HuffmanTree* tree)
   if(!error)
   {
     /*step 1: count number of instances of each code length*/
-    for(bits = 0; bits < tree->numcodes; bits++) blcount.data[tree->lengths[bits]]++;
+    for(unsigned bits = 0; bits != tree->numcodes; ++bits) ++blcount.data[tree->lengths[bits]];
     /*step 2: generate the nextcode values*/
-    for(bits = 1; bits <= tree->maxbitlen; bits++)
+    for(unsigned bits = 1; bits <= tree->maxbitlen; ++bits)
     {
       nextcode.data[bits] = (nextcode.data[bits - 1] + blcount.data[bits - 1]) << 1;
     }
     /*step 3: generate all the codes*/
-    for(n = 0; n < tree->numcodes; n++)
+    for(unsigned n = 0; n != tree->numcodes; ++n)
     {
-      if(tree->lengths[n] != 0) tree->tree1d[n] = nextcode.data[tree->lengths[n]]++;
+      if(tree->lengths[n] != 0) tree->tree1d[n] = ++nextcode.data[tree->lengths[n]];
     }
   }
 
@@ -651,7 +651,7 @@ static unsigned HuffmanTree_makeFromLengths(HuffmanTree* tree, const unsigned* b
   unsigned i;
   tree->lengths = (unsigned*)lodepng_malloc(numcodes * sizeof(unsigned));
   if(!tree->lengths) return 83; /*alloc fail*/
-  for(i = 0; i < numcodes; i++) tree->lengths[i] = bitlen[i];
+  for(i = 0; i != numcodes; ++i) tree->lengths[i] = bitlen[i];
   tree->numcodes = (unsigned)numcodes; /*number of symbols*/
   tree->maxbitlen = maxbitlen;
   return HuffmanTree_makeFromLengths2(tree);
@@ -690,20 +690,20 @@ static void coin_copy(Coin* c1, const Coin* c2)
 static void add_coins(Coin* c1, const Coin* c2)
 {
   size_t i;
-  for(i = 0; i < c2->symbols.size; i++) uivector_push_back(&c1->symbols, c2->symbols.data[i]);
+  for(i = 0; i != c2->symbols.size; ++i) uivector_push_back(&c1->symbols, c2->symbols.data[i]);
   c1->weight += c2->weight;
 }
 
 static void init_coins(Coin* coins, size_t num)
 {
   size_t i;
-  for(i = 0; i < num; i++) coin_init(&coins[i]);
+  for(i = 0; i != num; ++i) coin_init(&coins[i]);
 }
 
 static void cleanup_coins(Coin* coins, size_t num)
 {
   size_t i;
-  for(i = 0; i < num; i++) coin_cleanup(&coins[i]);
+  for(i = 0; i != num; ++i) coin_cleanup(&coins[i]);
 }
 
 static int coin_compare(const void* a, const void* b) {
@@ -716,13 +716,13 @@ static unsigned append_symbol_coins(Coin* coins, const unsigned* frequencies, un
 {
   unsigned i;
   unsigned j = 0; /*index of present symbols*/
-  for(i = 0; i < numcodes; i++)
+  for(i = 0; i != numcodes; ++i)
   {
     if(frequencies[i] != 0) /*only include symbols that are present*/
     {
       coins[j].weight = frequencies[i] / (float)sum;
       uivector_push_back(&coins[j].symbols, i);
-      j++;
+      ++j;
     }
   }
   return 0;
@@ -741,16 +741,16 @@ unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequen
 
   if(numcodes == 0) return 80; /*error: a tree of 0 symbols is not supposed to be made*/
 
-  for(i = 0; i < numcodes; i++)
+  for(i = 0; i != numcodes; ++i)
   {
     if(frequencies[i] > 0)
     {
-      numpresent++;
+      ++numpresent;
       sum += frequencies[i];
     }
   }
 
-  for(i = 0; i < numcodes; i++) lengths[i] = 0;
+  for(i = 0; i != numcodes; ++i) lengths[i] = 0;
 
   /*ensure at least two present symbols. There should be at least one symbol
   according to RFC 1951 section 3.2.7. To decoders incorrectly require two. To
@@ -763,7 +763,7 @@ unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequen
   }
   else if(numpresent == 1)
   {
-    for(i = 0; i < numcodes; i++)
+    for(i = 0; i != numcodes; ++i)
     {
       if(frequencies[i])
       {
@@ -797,7 +797,7 @@ unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequen
     if(!error)
     {
       unsigned numprev = 0;
-      for(j = 1; j <= maxbitlen && !error; j++) /*each of the remaining rows*/
+      for(j = 1; j <= maxbitlen && !error; ++j) /*each of the remaining rows*/
       {
         unsigned tempnum;
         Coin* tempcoins;
@@ -814,7 +814,7 @@ unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequen
         for(i = 0; i + 1 < numprev; i += 2)
         {
           /*merge prev_row[i] and prev_row[i + 1] into new coin*/
-          Coin* coin = &coins[numcoins++];
+          Coin* coin = &coins[numcoins]++;
           coin_copy(coin, &prev_row[i]);
           add_coins(coin, &prev_row[i + 1]);
         }
@@ -831,10 +831,10 @@ unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequen
     if(!error)
     {
       /*calculate the lenghts of each symbol, as the amount of times a coin of each symbol is used*/
-      for(i = 0; i < numpresent - 1; i++)
+      for(i = 0; i != numpresent - 1; ++i)
       {
         Coin* coin = &coins[i];
-        for(j = 0; j < coin->symbols.size; j++) lengths[coin->symbols.data[j]]++;
+        for(j = 0; j < coin->symbols.size; j++) ++lengths[coin->symbols.data[j]];
       }
     }
 
@@ -884,10 +884,10 @@ static unsigned generateFixedLitLenTree(HuffmanTree* tree)
   if(!bitlen) return 83; /*alloc fail*/
 
   /*288 possible codes: 0-255=literals, 256=endcode, 257-285=lengthcodes, 286-287=unused*/
-  for(i =   0; i <= 143; i++) bitlen[i] = 8;
-  for(i = 144; i <= 255; i++) bitlen[i] = 9;
-  for(i = 256; i <= 279; i++) bitlen[i] = 7;
-  for(i = 280; i <= 287; i++) bitlen[i] = 8;
+  for(i =   0; i <= 143; ++i) bitlen[i] = 8;
+  for(i = 144; i <= 255; ++i) bitlen[i] = 9;
+  for(i = 256; i <= 279; ++i) bitlen[i] = 7;
+  for(i = 280; i <= 287; ++i) bitlen[i] = 8;
 
   error = HuffmanTree_makeFromLengths(tree, bitlen, NUM_DEFLATE_CODE_SYMBOLS, 15);
 
@@ -903,7 +903,7 @@ static unsigned generateFixedDistanceTree(HuffmanTree* tree)
   if(!bitlen) return 83; /*alloc fail*/
 
   /*there are 32 distance codes, but 30-31 are unused*/
-  for(i = 0; i < NUM_DISTANCE_SYMBOLS; i++) bitlen[i] = 5;
+  for(i = 0; i != NUM_DISTANCE_SYMBOLS; ++i) bitlen[i] = 5;
   error = HuffmanTree_makeFromLengths(tree, bitlen, NUM_DISTANCE_SYMBOLS, 15);
 
   lodepng_free(bitlen);
@@ -928,7 +928,7 @@ static unsigned huffmanDecodeSymbol(const unsigned char* in, size_t* bp,
     the expression below because this is the biggest bottleneck while decoding
     */
     ct = codetree->tree2d[(treepos << 1) + READBIT(*bp, in)];
-    (*bp)++;
+    ++(*bp);
     if(ct < codetree->numcodes) return ct; /*the symbol is decoded, return it*/
     else treepos = ct - codetree->numcodes; /*symbol not yet decoded, instead move tree position*/
 
@@ -985,7 +985,7 @@ static unsigned getTreeInflateDynamic(HuffmanTree* tree_ll, HuffmanTree* tree_d,
     bitlen_cl = (unsigned*)lodepng_malloc(NUM_CODE_LENGTH_CODES * sizeof(unsigned));
     if(!bitlen_cl) ERROR_BREAK(83 /*alloc fail*/);
 
-    for(i = 0; i < NUM_CODE_LENGTH_CODES; i++)
+    for(i = 0; i != NUM_CODE_LENGTH_CODES; ++i)
     {
       if(i < HCLEN) bitlen_cl[CLCL_ORDER[i]] = readBitsFromStream(bp, in, 3);
       else bitlen_cl[CLCL_ORDER[i]] = 0; /*if not, it must stay 0*/
@@ -998,8 +998,8 @@ static unsigned getTreeInflateDynamic(HuffmanTree* tree_ll, HuffmanTree* tree_d,
     bitlen_ll = (unsigned*)lodepng_malloc(NUM_DEFLATE_CODE_SYMBOLS * sizeof(unsigned));
     bitlen_d = (unsigned*)lodepng_malloc(NUM_DISTANCE_SYMBOLS * sizeof(unsigned));
     if(!bitlen_ll || !bitlen_d) ERROR_BREAK(83 /*alloc fail*/);
-    for(i = 0; i < NUM_DEFLATE_CODE_SYMBOLS; i++) bitlen_ll[i] = 0;
-    for(i = 0; i < NUM_DISTANCE_SYMBOLS; i++) bitlen_d[i] = 0;
+    for(i = 0; i != NUM_DEFLATE_CODE_SYMBOLS; ++i) bitlen_ll[i] = 0;
+    for(i = 0; i != NUM_DISTANCE_SYMBOLS; ++i) bitlen_d[i] = 0;
 
     /*i is the current symbol we're reading in the part that contains the code lengths of lit/len and dist codes*/
     i = 0;
@@ -1010,7 +1010,7 @@ static unsigned getTreeInflateDynamic(HuffmanTree* tree_ll, HuffmanTree* tree_d,
       {
         if(i < HLIT) bitlen_ll[i] = code;
         else bitlen_d[i - HLIT] = code;
-        i++;
+        ++i;
       }
       else if(code == 16) /*repeat previous*/
       {
@@ -1030,7 +1030,7 @@ static unsigned getTreeInflateDynamic(HuffmanTree* tree_ll, HuffmanTree* tree_d,
           if(i >= HLIT + HDIST) ERROR_BREAK(13); /*error: i is larger than the amount of codes*/
           if(i < HLIT) bitlen_ll[i] = value;
           else bitlen_d[i - HLIT] = value;
-          i++;
+          ++i;
         }
       }
       else if(code == 17) /*repeat "0" 3-10 times*/
@@ -1047,7 +1047,7 @@ static unsigned getTreeInflateDynamic(HuffmanTree* tree_ll, HuffmanTree* tree_d,
 
           if(i < HLIT) bitlen_ll[i] = 0;
           else bitlen_d[i - HLIT] = 0;
-          i++;
+          ++i;
         }
       }
       else if(code == 18) /*repeat "0" 11-138 times*/
@@ -1064,7 +1064,7 @@ static unsigned getTreeInflateDynamic(HuffmanTree* tree_ll, HuffmanTree* tree_d,
 
           if(i < HLIT) bitlen_ll[i] = 0;
           else bitlen_d[i - HLIT] = 0;
-          i++;
+          ++i;
         }
       }
       else /*if(code == (unsigned)(-1))*/ /*huffmanDecodeSymbol returns (unsigned)(-1) in case of error*/
@@ -1123,7 +1123,7 @@ static unsigned inflateHuffmanBlock(ucvector* out, const unsigned char* in, size
       /*ucvector_push_back would do the same, but for some reason the two lines below run 10% faster*/
       if(!ucvector_resize(out, (*pos) + 1)) ERROR_BREAK(83 /*alloc fail*/);
       out->data[*pos] = (unsigned char)code_ll;
-      (*pos)++;
+      ++(*pos);
     }
     else if(code_ll >= FIRST_LENGTH_CODE_INDEX && code_ll <= LAST_LENGTH_CODE_INDEX) /*length code*/
     {
@@ -1169,8 +1169,8 @@ static unsigned inflateHuffmanBlock(ucvector* out, const unsigned char* in, size
       for(forward = 0; forward < length; forward++)
       {
         out->data[(*pos)] = out->data[backward];
-        (*pos)++;
-        backward++;
+        ++(*pos);
+        ++backward;
         if(backward >= start) backward = start - distance;
       }
     }
@@ -1198,7 +1198,7 @@ static unsigned inflateNoCompression(ucvector* out, const unsigned char* in, siz
   /*go to first boundary of byte*/
   size_t p;
   unsigned LEN, NLEN, n, error = 0;
-  while(((*bp) & 0x7) != 0) (*bp)++;
+  while(((*bp) & 0x7) != 0) ++(*bp);
   p = (*bp) / 8; /*byte position*/
 
   /*read LEN (2 bytes) and NLEN (2 bytes)*/
@@ -1298,7 +1298,7 @@ given array must be sorted (if no value is smaller, it returns the size of the g
 static size_t searchCodeIndex(const unsigned* array, size_t array_size, size_t value)
 {
   /*linear search implementation*/
-  /*for(size_t i = 1; i < array_size; i++) if(array[i] > value) return i - 1;
+  /*for(size_t i = 1; i < array_size; ++i) if(array[i] > value) return i - 1;
   return array_size - 1;*/
 
   /*binary search implementation (not that much faster) (precondition: array_size > 0)*/
@@ -1369,12 +1369,12 @@ static unsigned hash_init(Hash* hash, unsigned windowsize)
   }
 
   /*initialize hash table*/
-  for(i = 0; i < HASH_NUM_VALUES; i++) hash->head[i] = -1;
-  for(i = 0; i < windowsize; i++) hash->val[i] = -1;
-  for(i = 0; i < windowsize; i++) hash->chain[i] = i; /*same value as index indicates uninitialized*/
+  for(i = 0; i != HASH_NUM_VALUES; ++i) hash->head[i] = -1;
+  for(i = 0; i != windowsize; ++i) hash->val[i] = -1;
+  for(i = 0; i != windowsize; ++i) hash->chain[i] = i; /*same value as index indicates uninitialized*/
 
-  for(i = 0; i <= MAX_SUPPORTED_DEFLATE_LENGTH; i++) hash->headz[i] = -1;
-  for(i = 0; i < windowsize; i++) hash->chainz[i] = i; /*same value as index indicates uninitialized*/
+  for(i = 0; i <= MAX_SUPPORTED_DEFLATE_LENGTH; ++i) hash->headz[i] = -1;
+  for(i = 0; i != windowsize; ++i) hash->chainz[i] = i; /*same value as index indicates uninitialized*/
 
   return 0;
 }
@@ -1408,7 +1408,7 @@ static unsigned getHash(const unsigned char* data, size_t size, size_t pos)
     size_t amount, i;
     if(pos >= size) return 0;
     amount = size - pos;
-    for(i = 0; i < amount; i++) result ^= (unsigned)(data[pos + i] << (i * 8u));
+    for(i = 0; i != amount; ++i) result ^= (unsigned)(data[pos + i] << (i * 8u));
   }
   return result & HASH_BIT_MASK;
 }
@@ -1419,7 +1419,7 @@ static unsigned countZeros(const unsigned char* data, size_t size, size_t pos)
   const unsigned char* end = start + MAX_SUPPORTED_DEFLATE_LENGTH;
   if(end > data + size) end = data + size;
   data = start;
-  while (data != end && *data == 0) data++;
+  while (data != end && *data == 0) ++data;
   /*subtracting two addresses returned as 32-bit number (max value is MAX_SUPPORTED_DEFLATE_LENGTH)*/
   return (unsigned)(data - start);
 }
@@ -1542,7 +1542,7 @@ static unsigned encodeLZ77(uivector* out, Hash* hash,
       }
 
       if(hashpos == hash->chain[hashpos]) break;
-      
+
       if(numzeros >= 3 && length > numzeros) {
         hashpos = hash->chainz[hashpos];
         if(hash->zeros[hashpos] != numzeros) break;
@@ -1597,9 +1597,9 @@ static unsigned encodeLZ77(uivector* out, Hash* hash,
     else
     {
       addLengthDistance(out, length, offset);
-      for(i = 1; i < length; i++)
+      for(i = 1; i < length; ++i)
       {
-        pos++;
+        ++pos;
         wpos = pos & (windowsize - 1);
         hashval = getHash(in, insize, pos);
         if(usezeros && hashval == 0)
@@ -1628,7 +1628,7 @@ static unsigned deflateNoCompression(ucvector* out, const unsigned char* data, s
 
   size_t i, j, numdeflateblocks = (datasize + 65534) / 65535;
   unsigned datapos = 0;
-  for(i = 0; i < numdeflateblocks; i++)
+  for(i = 0; i != numdeflateblocks; ++i)
   {
     unsigned BFINAL, BTYPE, LEN, NLEN;
     unsigned char firstbyte;
@@ -1667,7 +1667,7 @@ static void writeLZ77data(size_t* bp, ucvector* out, const uivector* lz77_encode
                           const HuffmanTree* tree_ll, const HuffmanTree* tree_d)
 {
   size_t i = 0;
-  for(i = 0; i < lz77_encoded->size; i++)
+  for(i = 0; i != lz77_encoded->size; ++i)
   {
     unsigned val = lz77_encoded->data[i];
     addHuffmanSymbol(bp, out, HuffmanTree_getCode(tree_ll, val), HuffmanTree_getLength(tree_ll, val));
@@ -1760,21 +1760,21 @@ static unsigned deflateDynamic(ucvector* out, size_t* bp, Hash* hash,
     else
     {
       if(!uivector_resize(&lz77_encoded, datasize)) ERROR_BREAK(83 /*alloc fail*/);
-      for(i = datapos; i < dataend; i++) lz77_encoded.data[i] = data[i]; /*no LZ77, but still will be Huffman compressed*/
+      for(i = datapos; i < dataend; ++i) lz77_encoded.data[i] = data[i]; /*no LZ77, but still will be Huffman compressed*/
     }
 
     if(!uivector_resizev(&frequencies_ll, 286, 0)) ERROR_BREAK(83 /*alloc fail*/);
     if(!uivector_resizev(&frequencies_d, 30, 0)) ERROR_BREAK(83 /*alloc fail*/);
 
     /*Count the frequencies of lit, len and dist codes*/
-    for(i = 0; i < lz77_encoded.size; i++)
+    for(i = 0; i != lz77_encoded.size; ++i)
     {
       unsigned symbol = lz77_encoded.data[i];
-      frequencies_ll.data[symbol]++;
+      ++frequencies_ll.data[symbol];
       if(symbol > 256)
       {
         unsigned dist = lz77_encoded.data[i + 2];
-        frequencies_d.data[dist]++;
+        ++frequencies_d.data[dist];
         i += 3;
       }
     }
@@ -1790,15 +1790,15 @@ static unsigned deflateDynamic(ucvector* out, size_t* bp, Hash* hash,
     numcodes_ll = tree_ll.numcodes; if(numcodes_ll > 286) numcodes_ll = 286;
     numcodes_d = tree_d.numcodes; if(numcodes_d > 30) numcodes_d = 30;
     /*store the code lengths of both generated trees in bitlen_lld*/
-    for(i = 0; i < numcodes_ll; i++) uivector_push_back(&bitlen_lld, HuffmanTree_getLength(&tree_ll, (unsigned)i));
-    for(i = 0; i < numcodes_d; i++) uivector_push_back(&bitlen_lld, HuffmanTree_getLength(&tree_d, (unsigned)i));
+    for(i = 0; i != numcodes_ll; ++i) uivector_push_back(&bitlen_lld, HuffmanTree_getLength(&tree_ll, (unsigned)i));
+    for(i = 0; i != numcodes_d; ++i) uivector_push_back(&bitlen_lld, HuffmanTree_getLength(&tree_d, (unsigned)i));
 
     /*run-length compress bitlen_ldd into bitlen_lld_e by using repeat codes 16 (copy length 3-6 times),
     17 (3-10 zeroes), 18 (11-138 zeroes)*/
-    for(i = 0; i < (unsigned)bitlen_lld.size; i++)
+    for(i = 0; i != (unsigned)bitlen_lld.size; ++i)
     {
       unsigned j = 0; /*amount of repititions*/
-      while(i + j + 1 < (unsigned)bitlen_lld.size && bitlen_lld.data[i + j + 1] == bitlen_lld.data[i]) j++;
+      while(i + j + 1 < (unsigned)bitlen_lld.size && bitlen_lld.data[i + j + 1] == bitlen_lld.data[i]) ++j;
 
       if(bitlen_lld.data[i] == 0 && j >= 2) /*repeat code for zeroes*/
       {
@@ -1843,7 +1843,7 @@ static unsigned deflateDynamic(ucvector* out, size_t* bp, Hash* hash,
     /*generate tree_cl, the huffmantree of huffmantrees*/
 
     if(!uivector_resizev(&frequencies_cl, NUM_CODE_LENGTH_CODES, 0)) ERROR_BREAK(83 /*alloc fail*/);
-    for(i = 0; i < bitlen_lld_e.size; i++)
+    for(i = 0; i != bitlen_lld_e.size; ++i)
     {
       frequencies_cl.data[bitlen_lld_e.data[i]]++;
       /*after a repeat code come the bits that specify the number of repetitions,
@@ -1856,7 +1856,7 @@ static unsigned deflateDynamic(ucvector* out, size_t* bp, Hash* hash,
     if(error) break;
 
     if(!uivector_resize(&bitlen_cl, tree_cl.numcodes)) ERROR_BREAK(83 /*alloc fail*/);
-    for(i = 0; i < tree_cl.numcodes; i++)
+    for(i = 0; i != tree_cl.numcodes; ++i)
     {
       /*lenghts of code length tree is in the order as specified by deflate*/
       bitlen_cl.data[i] = HuffmanTree_getLength(&tree_cl, CLCL_ORDER[i]);
@@ -1898,10 +1898,10 @@ static unsigned deflateDynamic(ucvector* out, size_t* bp, Hash* hash,
     addBitsToStream(bp, out, HCLEN, 4);
 
     /*write the code lenghts of the code length alphabet*/
-    for(i = 0; i < HCLEN + 4; i++) addBitsToStream(bp, out, bitlen_cl.data[i], 3);
+    for(i = 0; i != HCLEN + 4; ++i) addBitsToStream(bp, out, bitlen_cl.data[i], 3);
 
     /*write the lenghts of the lit/len AND the dist alphabet*/
-    for(i = 0; i < bitlen_lld_e.size; i++)
+    for(i = 0; i != bitlen_lld_e.size; ++i)
     {
       addHuffmanSymbol(bp, out, HuffmanTree_getCode(&tree_cl, bitlen_lld_e.data[i]),
                        HuffmanTree_getLength(&tree_cl, bitlen_lld_e.data[i]));
@@ -1947,7 +1947,6 @@ static unsigned deflateFixed(ucvector* out, size_t* bp, Hash* hash,
 
   unsigned BFINAL = final;
   unsigned error = 0;
-  size_t i;
 
   HuffmanTree_init(&tree_ll);
   HuffmanTree_init(&tree_d);
@@ -1970,7 +1969,7 @@ static unsigned deflateFixed(ucvector* out, size_t* bp, Hash* hash,
   }
   else /*no LZ77, but still will be Huffman compressed*/
   {
-    for(i = datapos; i < dataend; i++)
+    for(size_t i = datapos; i < dataend; ++i)
     {
       addHuffmanSymbol(bp, out, HuffmanTree_getCode(&tree_ll, data[i]), HuffmanTree_getLength(&tree_ll, data[i]));
     }
@@ -2008,7 +2007,7 @@ static unsigned lodepng_deflatev(ucvector* out, const unsigned char* in, size_t
   error = hash_init(&hash, settings->windowsize);
   if(error) return error;
 
-  for(i = 0; i < numdeflateblocks && !error; i++)
+  for(i = 0; i != numdeflateblocks && !error; ++i)
   {
     unsigned final = (i == numdeflateblocks - 1);
     size_t start = i * blocksize;
@@ -2160,12 +2159,10 @@ unsigned lodepng_zlib_compress(unsigned char** out, size_t* outsize, const unsig
   /*initially, *out must be NULL and outsize 0, if you just give some random *out
   that's pointing to a non allocated buffer, this'll crash*/
   ucvector outv;
-  size_t i;
   unsigned error;
   unsigned char* deflatedata = 0;
   size_t deflatesize = 0;
 
-  unsigned ADLER32;
   /*zlib data: 1 byte CMF (CM+CINFO), 1 byte FLG, deflate data, 4 byte ADLER32 checksum of the Decompressed data*/
   unsigned CMF = 120; /*0b01111000: CM 8, CINFO 7. With CINFO 7, any window size up to 32768 can be used.*/
   unsigned FLEVEL = 0;
@@ -2184,8 +2181,8 @@ unsigned lodepng_zlib_compress(unsigned char** out, size_t* outsize, const unsig
 
   if(!error)
   {
-    ADLER32 = adler32(in, (unsigned)insize);
-    for(i = 0; i < deflatesize; i++) ucvector_push_back(&outv, deflatedata[i]);
+    unsigned ADLER32 = adler32(in, (unsigned)insize);
+    for(size_t i = 0; i != deflatesize; ++i) ucvector_push_back(&outv, deflatedata[i]);
     lodepng_free(deflatedata);
     lodepng_add32bitInt(&outv, ADLER32);
   }
@@ -2350,8 +2347,7 @@ static unsigned char readBitFromReversedStream(size_t* bitpointer, const unsigne
 static unsigned readBitsFromReversedStream(size_t* bitpointer, const unsigned char* bitstream, size_t nbits)
 {
   unsigned result = 0;
-  size_t i;
-  for(i = nbits - 1; i < nbits; i--)
+  for(size_t i = nbits - 1; i < nbits; --i)
   {
     result += (unsigned)readBitFromReversedStream(bitpointer, bitstream) << i;
   }
@@ -2391,7 +2387,7 @@ unsigned lodepng_chunk_length(const unsigned char* chunk)
 void lodepng_chunk_type(char type[5], const unsigned char* chunk)
 {
   unsigned i;
-  for(i = 0; i < 4; i++) type[i] = (char)chunk[4 + i];
+  for(i = 0; i != 4; ++i) type[i] = (char)chunk[4 + i];
   type[4] = 0; /*null termination char*/
 }
 
@@ -2469,7 +2465,7 @@ unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsi
   (*outlength) = new_length;
   chunk_start = &(*out)[new_length - total_chunk_length];
 
-  for(i = 0; i < total_chunk_length; i++) chunk_start[i] = chunk[i];
+  for(i = 0; i != total_chunk_length; ++i) chunk_start[i] = chunk[i];
 
   return 0;
 }
@@ -2497,7 +2493,7 @@ unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned l
   chunk[7] = (unsigned char)type[3];
 
   /*3: the data*/
-  for(i = 0; i < length; i++) chunk[8 + i] = data[i];
+  for(i = 0; i != length; ++i) chunk[8 + i] = data[i];
 
   /*4: CRC (of the chunkname characters and the data)*/
   lodepng_chunk_generate_crc(chunk);
@@ -2562,14 +2558,13 @@ void lodepng_color_mode_cleanup(LodePNGColorMode* info)
 
 unsigned lodepng_color_mode_copy(LodePNGColorMode* dest, const LodePNGColorMode* source)
 {
-  size_t i;
   lodepng_color_mode_cleanup(dest);
   *dest = *source;
   if(source->palette)
   {
     dest->palette = (unsigned char*)lodepng_malloc(1024);
     if(!dest->palette && source->palettesize) return 83; /*alloc fail*/
-    for(i = 0; i < source->palettesize * 4; i++) dest->palette[i] = source->palette[i];
+    for(size_t i = 0; i != source->palettesize * 4; ++i) dest->palette[i] = source->palette[i];
   }
   return 0;
 }
@@ -2587,7 +2582,7 @@ static int lodepng_color_mode_equal(const LodePNGColorMode* a, const LodePNGColo
     if(a->key_b != b->key_b) return 0;
   }
   if(a->palettesize != b->palettesize) return 0;
-  for(i = 0; i < a->palettesize * 4; i++)
+  for(i = 0; i != a->palettesize * 4; ++i)
   {
     if(a->palette[i] != b->palette[i]) return 0;
   }
@@ -2651,7 +2646,7 @@ unsigned lodepng_is_palette_type(const LodePNGColorMode* info)
 unsigned lodepng_has_palette_alpha(const LodePNGColorMode* info)
 {
   size_t i;
-  for(i = 0; i < info->palettesize; i++)
+  for(i = 0; i != info->palettesize; ++i)
   {
     if(info->palette[i * 4 + 3] < 255) return 1;
   }
@@ -2691,14 +2686,14 @@ static size_t lodepng_get_raw_size_idat(unsigned w, unsigned h, const LodePNGCol
 static void LodePNGUnknownChunks_init(LodePNGInfo* info)
 {
   unsigned i;
-  for(i = 0; i < 3; i++) info->unknown_chunks_data[i] = 0;
-  for(i = 0; i < 3; i++) info->unknown_chunks_size[i] = 0;
+  for(i = 0; i != 3; ++i) info->unknown_chunks_data[i] = 0;
+  for(i = 0; i != 3; ++i) info->unknown_chunks_size[i] = 0;
 }
 
 static void LodePNGUnknownChunks_cleanup(LodePNGInfo* info)
 {
   unsigned i;
-  for(i = 0; i < 3; i++) lodepng_free(info->unknown_chunks_data[i]);
+  for(i = 0; i != 3; ++i) lodepng_free(info->unknown_chunks_data[i]);
 }
 
 static unsigned LodePNGUnknownChunks_copy(LodePNGInfo* dest, const LodePNGInfo* src)
@@ -2707,7 +2702,7 @@ static unsigned LodePNGUnknownChunks_copy(LodePNGInfo* dest, const LodePNGInfo*
 
   LodePNGUnknownChunks_cleanup(dest);
 
-  for(i = 0; i < 3; i++)
+  for(i = 0; i != 3; ++i)
   {
     size_t j;
     dest->unknown_chunks_size[i] = src->unknown_chunks_size[i];
@@ -2734,7 +2729,7 @@ static void LodePNGText_init(LodePNGInfo* info)
 static void LodePNGText_cleanup(LodePNGInfo* info)
 {
   size_t i;
-  for(i = 0; i < info->text_num; i++)
+  for(i = 0; i != info->text_num; ++i)
   {
     string_cleanup(&info->text_keys[i]);
     string_cleanup(&info->text_strings[i]);
@@ -2749,7 +2744,7 @@ static unsigned LodePNGText_copy(LodePNGInfo* dest, const LodePNGInfo* source)
   dest->text_keys = 0;
   dest->text_strings = 0;
   dest->text_num = 0;
-  for(i = 0; i < source->text_num; i++)
+  for(i = 0; i != source->text_num; ++i)
   {
     CERROR_TRY_RETURN(lodepng_add_text(dest, source->text_keys[i], source->text_strings[i]));
   }
@@ -2799,7 +2794,7 @@ static void LodePNGIText_init(LodePNGInfo* info)
 static void LodePNGIText_cleanup(LodePNGInfo* info)
 {
   size_t i;
-  for(i = 0; i < info->itext_num; i++)
+  for(i = 0; i != info->itext_num; ++i)
   {
     string_cleanup(&info->itext_keys[i]);
     string_cleanup(&info->itext_langtags[i]);
@@ -2820,7 +2815,7 @@ static unsigned LodePNGIText_copy(LodePNGInfo* dest, const LodePNGInfo* source)
   dest->itext_transkeys = 0;
   dest->itext_strings = 0;
   dest->itext_num = 0;
-  for(i = 0; i < source->itext_num; i++)
+  for(i = 0; i != source->itext_num; ++i)
   {
     CERROR_TRY_RETURN(lodepng_add_itext(dest, source->itext_keys[i], source->itext_langtags[i],
                                         source->itext_transkeys[i], source->itext_strings[i]));
@@ -2957,14 +2952,14 @@ struct ColorTree
 static void color_tree_init(ColorTree* tree)
 {
   int i;
-  for(i = 0; i < 16; i++) tree->children[i] = 0;
+  for(i = 0; i != 16; ++i) tree->children[i] = 0;
   tree->index = -1;
 }
 
 static void color_tree_cleanup(ColorTree* tree)
 {
   int i;
-  for(i = 0; i < 16; i++)
+  for(i = 0; i != 16; ++i)
   {
     if(tree->children[i])
     {
@@ -3249,7 +3244,7 @@ static void getPixelColorsRGBA8(unsigned char* buffer, size_t numpixels,
   {
     if(mode->bitdepth == 8)
     {
-      for(i = 0; i < numpixels; i++, buffer += num_channels)
+      for(i = 0; i != numpixels; i++, buffer += num_channels)
       {
         buffer[0] = buffer[1] = buffer[2] = in[i];
         if(has_alpha) buffer[3] = mode->key_defined && in[i] == mode->key_r ? 0 : 255;
@@ -3257,7 +3252,7 @@ static void getPixelColorsRGBA8(unsigned char* buffer, size_t numpixels,
     }
     else if(mode->bitdepth == 16)
     {
-      for(i = 0; i < numpixels; i++, buffer += num_channels)
+      for(i = 0; i != numpixels; i++, buffer += num_channels)
       {
         buffer[0] = buffer[1] = buffer[2] = in[i * 2];
         if(has_alpha) buffer[3] = mode->key_defined && 256U * in[i * 2 + 0] + in[i * 2 + 1] == mode->key_r ? 0 : 255;
@@ -3267,7 +3262,7 @@ static void getPixelColorsRGBA8(unsigned char* buffer, size_t numpixels,
     {
       unsigned highest = ((1U << mode->bitdepth) - 1U); /*highest possible value for this bit depth*/
       size_t j = 0;
-      for(i = 0; i < numpixels; i++, buffer += num_channels)
+      for(i = 0; i != numpixels; i++, buffer += num_channels)
       {
         unsigned value = readBitsFromReversedStream(&j, in, mode->bitdepth);
         buffer[0] = buffer[1] = buffer[2] = (value * 255) / highest;
@@ -3279,7 +3274,7 @@ static void getPixelColorsRGBA8(unsigned char* buffer, size_t numpixels,
   {
     if(mode->bitdepth == 8)
     {
-      for(i = 0; i < numpixels; i++, buffer += num_channels)
+      for(i = 0; i != numpixels; i++, buffer += num_channels)
       {
         buffer[0] = in[i * 3 + 0];
         buffer[1] = in[i * 3 + 1];
@@ -3290,7 +3285,7 @@ static void getPixelColorsRGBA8(unsigned char* buffer, size_t numpixels,
     }
     else
     {
-      for(i = 0; i < numpixels; i++, buffer += num_channels)
+      for(i = 0; i != numpixels; i++, buffer += num_channels)
       {
         buffer[0] = in[i * 6 + 0];
         buffer[1] = in[i * 6 + 2];
@@ -3306,7 +3301,7 @@ static void getPixelColorsRGBA8(unsigned char* buffer, size_t numpixels,
   {
     unsigned index;
     size_t j = 0;
-    for(i = 0; i < numpixels; i++, buffer += num_channels)
+    for(i = 0; i != numpixels; i++, buffer += num_channels)
     {
       if(mode->bitdepth == 8) index = in[i];
       else index = readBitsFromReversedStream(&j, in, mode->bitdepth);
@@ -3331,7 +3326,7 @@ static void getPixelColorsRGBA8(unsigned char* buffer, size_t numpixels,
   {
     if(mode->bitdepth == 8)
     {
-      for(i = 0; i < numpixels; i++, buffer += num_channels)
+      for(i = 0; i != numpixels; i++, buffer += num_channels)
       {
         buffer[0] = buffer[1] = buffer[2] = in[i * 2 + 0];
         if(has_alpha) buffer[3] = in[i * 2 + 1];
@@ -3339,7 +3334,7 @@ static void getPixelColorsRGBA8(unsigned char* buffer, size_t numpixels,
     }
     else
     {
-      for(i = 0; i < numpixels; i++, buffer += num_channels)
+      for(i = 0; i != numpixels; i++, buffer += num_channels)
       {
         buffer[0] = buffer[1] = buffer[2] = in[i * 4 + 0];
         if(has_alpha) buffer[3] = in[i * 4 + 2];
@@ -3350,7 +3345,7 @@ static void getPixelColorsRGBA8(unsigned char* buffer, size_t numpixels,
   {
     if(mode->bitdepth == 8)
     {
-      for(i = 0; i < numpixels; i++, buffer += num_channels)
+      for(i = 0; i != numpixels; i++, buffer += num_channels)
       {
         buffer[0] = in[i * 4 + 0];
         buffer[1] = in[i * 4 + 1];
@@ -3360,7 +3355,7 @@ static void getPixelColorsRGBA8(unsigned char* buffer, size_t numpixels,
     }
     else
     {
-      for(i = 0; i < numpixels; i++, buffer += num_channels)
+      for(i = 0; i != numpixels; i++, buffer += num_channels)
       {
         buffer[0] = in[i * 8 + 0];
         buffer[1] = in[i * 8 + 2];
@@ -3417,7 +3412,7 @@ unsigned lodepng_convert(unsigned char* out, const unsigned char* in,
   if(lodepng_color_mode_equal(mode_out, mode_in))
   {
     size_t numbytes = lodepng_get_raw_size(w, h, mode_in);
-    for(i = 0; i < numbytes; i++) out[i] = in[i];
+    for(i = 0; i != numbytes; ++i) out[i] = in[i];
     return 0;
   }
 
@@ -3426,7 +3421,7 @@ unsigned lodepng_convert(unsigned char* out, const unsigned char* in,
     size_t palsize = 1u << mode_out->bitdepth;
     if(mode_out->palettesize < palsize) palsize = mode_out->palettesize;
     color_tree_init(&tree);
-    for(i = 0; i < palsize; i++)
+    for(i = 0; i != palsize; ++i)
     {
       unsigned char* p = &mode_out->palette[i * 4];
       color_tree_add(&tree, p[0], p[1], p[2], p[3], i);
@@ -3435,7 +3430,7 @@ unsigned lodepng_convert(unsigned char* out, const unsigned char* in,
 
   if(mode_in->bitdepth == 16 && mode_out->bitdepth == 16)
   {
-    for(i = 0; i < numpixels; i++)
+    for(i = 0; i != numpixels; ++i)
     {
       unsigned short r = 0, g = 0, b = 0, a = 0;
       getPixelColorRGBA16(&r, &g, &b, &a, in, i, mode_in);
@@ -3453,7 +3448,7 @@ unsigned lodepng_convert(unsigned char* out, const unsigned char* in,
   else
   {
     unsigned char r = 0, g = 0, b = 0, a = 0;
-    for(i = 0; i < numpixels; i++)
+    for(i = 0; i != numpixels; ++i)
     {
       getPixelColorRGBA8(&r, &g, &b, &a, in, i, mode_in);
       rgba8ToPixel(out, i, mode_out, &tree, r, g, b, a);
@@ -3528,7 +3523,7 @@ unsigned get_color_profile(LodePNGColorProfile* profile,
   if(mode->bitdepth == 16)
   {
     unsigned short r, g, b, a;
-    for(i = 0; i < numpixels; i++)
+    for(i = 0; i != numpixels; ++i)
     {
       getPixelColorRGBA16(&r, &g, &b, &a, in, i, mode);
       if(r % 257u != 0 || g % 257u != 0 || b % 257u != 0 || a % 257u != 0) /*first and second byte differ*/
@@ -3545,10 +3540,10 @@ unsigned get_color_profile(LodePNGColorProfile* profile,
     profile->bits = 16;
     bits_done = numcolors_done = 1; /*counting colors no longer useful, palette doesn't support 16-bit*/
 
-    for(i = 0; i < numpixels; i++)
+    for(i = 0; i != numpixels; ++i)
     {
       getPixelColorRGBA16(&r, &g, &b, &a, in, i, mode);
-      
+
       if(!colored_done && (r != g || r != b))
       {
         profile->colored = 1;
@@ -3584,7 +3579,7 @@ unsigned get_color_profile(LodePNGColorProfile* profile,
   }
   else /* < 16-bit */
   {
-    for(i = 0; i < numpixels; i++)
+    for(i = 0; i != numpixels; ++i)
     {
       unsigned char r = 0, g = 0, b = 0, a = 0;
       getPixelColorRGBA8(&r, &g, &b, &a, in, i, mode);
@@ -3672,7 +3667,7 @@ unsigned lodepng_auto_choose_color(LodePNGColorMode* mode_out,
 {
   LodePNGColorProfile prof;
   unsigned error = 0;
-  unsigned i, n, palettebits, grey_ok, palette_ok;
+  unsigned n, palettebits, grey_ok, palette_ok;
 
   lodepng_color_profile_init(&prof);
   error = get_color_profile(&prof, image, w, h, mode_in);
@@ -3691,7 +3686,7 @@ unsigned lodepng_auto_choose_color(LodePNGColorMode* mode_out,
   {
     unsigned char* p = prof.palette;
     lodepng_palette_clear(mode_out); /*remove potential earlier palette*/
-    for(i = 0; i < prof.numcolors; i++)
+    for(unsigned i = 0; i != prof.numcolors; ++i)
     {
       error = lodepng_palette_add(mode_out, p[i * 4 + 0], p[i * 4 + 1], p[i * 4 + 2], p[i * 4 + 3]);
       if(error) break;
@@ -3774,7 +3769,7 @@ static void Adam7_getpassvalues(unsigned passw[7], unsigned passh[7], size_t fil
   unsigned i;
 
   /*calculate width and height in pixels of each pass*/
-  for(i = 0; i < 7; i++)
+  for(i = 0; i != 7; ++i)
   {
     passw[i] = (w + ADAM7_DX[i] - ADAM7_IX[i] - 1) / ADAM7_DX[i];
     passh[i] = (h + ADAM7_DY[i] - ADAM7_IY[i] - 1) / ADAM7_DY[i];
@@ -3783,7 +3778,7 @@ static void Adam7_getpassvalues(unsigned passw[7], unsigned passh[7], size_t fil
   }
 
   filter_passstart[0] = padded_passstart[0] = passstart[0] = 0;
-  for(i = 0; i < 7; i++)
+  for(i = 0; i != 7; ++i)
   {
     /*if passw[i] is 0, it's 0 bytes, not 1 (no filtertype-byte)*/
     filter_passstart[i + 1] = filter_passstart[i]
@@ -3875,53 +3870,53 @@ static unsigned unfilterScanline(unsigned char* recon, const unsigned char* scan
   switch(filterType)
   {
     case 0:
-      for(i = 0; i < length; i++) recon[i] = scanline[i];
+      for(i = 0; i != length; ++i) recon[i] = scanline[i];
       break;
     case 1:
-      for(i = 0; i < bytewidth; i++) recon[i] = scanline[i];
-      for(i = bytewidth; i < length; i++) recon[i] = scanline[i] + recon[i - bytewidth];
+      for(i = 0; i != bytewidth; ++i) recon[i] = scanline[i];
+      for(i = bytewidth; i < length; ++i) recon[i] = scanline[i] + recon[i - bytewidth];
       break;
     case 2:
       if(precon)
       {
-        for(i = 0; i < length; i++) recon[i] = scanline[i] + precon[i];
+        for(i = 0; i != length; ++i) recon[i] = scanline[i] + precon[i];
       }
       else
       {
-        for(i = 0; i < length; i++) recon[i] = scanline[i];
+        for(i = 0; i != length; ++i) recon[i] = scanline[i];
       }
       break;
     case 3:
       if(precon)
       {
-        for(i = 0; i < bytewidth; i++) recon[i] = scanline[i] + precon[i] / 2;
-        for(i = bytewidth; i < length; i++) recon[i] = scanline[i] + ((recon[i - bytewidth] + precon[i]) / 2);
+        for(i = 0; i != bytewidth; ++i) recon[i] = scanline[i] + precon[i] / 2;
+        for(i = bytewidth; i < length; ++i) recon[i] = scanline[i] + ((recon[i - bytewidth] + precon[i]) / 2);
       }
       else
       {
-        for(i = 0; i < bytewidth; i++) recon[i] = scanline[i];
-        for(i = bytewidth; i < length; i++) recon[i] = scanline[i] + recon[i - bytewidth] / 2;
+        for(i = 0; i != bytewidth; ++i) recon[i] = scanline[i];
+        for(i = bytewidth; i < length; ++i) recon[i] = scanline[i] + recon[i - bytewidth] / 2;
       }
       break;
     case 4:
       if(precon)
       {
-        for(i = 0; i < bytewidth; i++)
+        for(i = 0; i != bytewidth; ++i)
         {
           recon[i] = (scanline[i] + precon[i]); /*paethPredictor(0, precon[i], 0) is always precon[i]*/
         }
-        for(i = bytewidth; i < length; i++)
+        for(i = bytewidth; i < length; ++i)
         {
           recon[i] = (scanline[i] + paethPredictor(recon[i - bytewidth], precon[i], precon[i - bytewidth]));
         }
       }
       else
       {
-        for(i = 0; i < bytewidth; i++)
+        for(i = 0; i != bytewidth; ++i)
         {
           recon[i] = scanline[i];
         }
-        for(i = bytewidth; i < length; i++)
+        for(i = bytewidth; i < length; ++i)
         {
           /*paethPredictor(recon[i - bytewidth], 0, 0) is always recon[i - bytewidth]*/
           recon[i] = (scanline[i] + recon[i - bytewidth]);
@@ -3985,7 +3980,7 @@ static void Adam7_deinterlace(unsigned char* out, const unsigned char* in, unsig
 
   if(bpp >= 8)
   {
-    for(i = 0; i < 7; i++)
+    for(i = 0; i != 7; ++i)
     {
       unsigned x, y, b;
       size_t bytewidth = bpp / 8;
@@ -4003,7 +3998,7 @@ static void Adam7_deinterlace(unsigned char* out, const unsigned char* in, unsig
   }
   else /*bpp < 8: Adam7 with pixels < 8 bit is a bit trickier: with bit pointers*/
   {
-    for(i = 0; i < 7; i++)
+    for(i = 0; i != 7; ++i)
     {
       unsigned x, y, b;
       unsigned ilinebits = bpp * passw[i];
@@ -4085,7 +4080,7 @@ static unsigned postProcessScanlines(unsigned char* out, unsigned char* in,
 
     Adam7_getpassvalues(passw, passh, filter_passstart, padded_passstart, passstart, w, h, bpp);
 
-    for(i = 0; i < 7; i++)
+    for(i = 0; i != 7; ++i)
     {
       CERROR_TRY_RETURN(unfilter(&in[padded_passstart[i]], &in[filter_passstart[i]], passw[i], passh[i], bpp));
       /*TODO: possible efficiency improvement: if in this reduced image the bits fit nicely in 1 scanline,
@@ -4107,7 +4102,7 @@ static unsigned postProcessScanlines(unsigned char* out, unsigned char* in,
 
 static unsigned readChunk_PLTE(LodePNGColorMode* color, const unsigned char* data, size_t chunkLength)
 {
-  unsigned pos = 0, i;
+  unsigned pos = 0;
   if(color->palette) lodepng_free(color->palette);
   color->palettesize = chunkLength / 3;
   color->palette = (unsigned char*)lodepng_malloc(4 * color->palettesize);
@@ -4118,7 +4113,7 @@ static unsigned readChunk_PLTE(LodePNGColorMode* color, const unsigned char* dat
   }
   if(color->palettesize > 256) return 38; /*error: palette too big*/
 
-  for(i = 0; i < color->palettesize; i++)
+  for(unsigned i = 0; i != color->palettesize; ++i)
   {
     color->palette[4 * i + 0] = data[pos++]; /*R*/
     color->palette[4 * i + 1] = data[pos++]; /*G*/
@@ -4131,13 +4126,12 @@ static unsigned readChunk_PLTE(LodePNGColorMode* color, const unsigned char* dat
 
 static unsigned readChunk_tRNS(LodePNGColorMode* color, const unsigned char* data, size_t chunkLength)
 {
-  unsigned i;
   if(color->colortype == LCT_PALETTE)
   {
     /*error: more alpha values given than there are palette entries*/
     if(chunkLength > color->palettesize) return 38;
 
-    for(i = 0; i < chunkLength; i++) color->palette[4 * i + 3] = data[i];
+    for(unsigned i = 0; i != chunkLength; ++i) color->palette[4 * i + 3] = data[i];
   }
   else if(color->colortype == LCT_GREY)
   {
@@ -4218,7 +4212,7 @@ static unsigned readChunk_tEXt(LodePNGInfo* info, const unsigned char* data, siz
     if(!key) CERROR_BREAK(error, 83); /*alloc fail*/
 
     key[length] = 0;
-    for(i = 0; i < length; i++) key[i] = (char)data[i];
+    for(i = 0; i != length; ++i) key[i] = (char)data[i];
 
     string2_begin = length + 1; /*skip keyword null terminator*/
 
@@ -4227,7 +4221,7 @@ static unsigned readChunk_tEXt(LodePNGInfo* info, const unsigned char* data, siz
     if(!str) CERROR_BREAK(error, 83); /*alloc fail*/
 
     str[length] = 0;
-    for(i = 0; i < length; i++) str[i] = (char)data[string2_begin + i];
+    for(i = 0; i != length; ++i) str[i] = (char)data[string2_begin + i];
 
     error = lodepng_add_text(info, key, str);
 
@@ -4263,7 +4257,7 @@ static unsigned readChunk_zTXt(LodePNGInfo* info, const LodePNGDecompressSetting
     if(!key) CERROR_BREAK(error, 83); /*alloc fail*/
 
     key[length] = 0;
-    for(i = 0; i < length; i++) key[i] = (char)data[i];
+    for(i = 0; i != length; ++i) key[i] = (char)data[i];
 
     if(data[length + 1] != 0) CERROR_BREAK(error, 72); /*the 0 byte indicating compression must be 0*/
 
@@ -4308,7 +4302,7 @@ static unsigned readChunk_iTXt(LodePNGInfo* info, const LodePNGDecompressSetting
     if(chunkLength < 5) CERROR_BREAK(error, 30); /*iTXt chunk too short*/
 
     /*read the key*/
-    for(length = 0; length < chunkLength && data[length] != 0; length++) ;
+    for(length = 0; length < chunkLength && data[length] != 0; ++length) ;
     if(length + 3 >= chunkLength) CERROR_BREAK(error, 75); /*no null termination char, corrupt?*/
     if(length < 1 || length > 79) CERROR_BREAK(error, 89); /*keyword too short or long*/
 
@@ -4316,7 +4310,7 @@ static unsigned readChunk_iTXt(LodePNGInfo* info, const LodePNGDecompressSetting
     if(!key) CERROR_BREAK(error, 83); /*alloc fail*/
 
     key[length] = 0;
-    for(i = 0; i < length; i++) key[i] = (char)data[i];
+    for(i = 0; i != length; ++i) key[i] = (char)data[i];
 
     /*read the compression method*/
     compressed = data[length + 1];
@@ -4328,24 +4322,24 @@ static unsigned readChunk_iTXt(LodePNGInfo* info, const LodePNGDecompressSetting
     /*read the langtag*/
     begin = length + 3;
     length = 0;
-    for(i = begin; i < chunkLength && data[i] != 0; i++) length++;
+    for(i = begin; i < chunkLength && data[i] != 0; ++i) ++length;
 
     langtag = (char*)lodepng_malloc(length + 1);
     if(!langtag) CERROR_BREAK(error, 83); /*alloc fail*/
 
     langtag[length] = 0;
-    for(i = 0; i < length; i++) langtag[i] = (char)data[begin + i];
+    for(i = 0; i != length; ++i) langtag[i] = (char)data[begin + i];
 
     /*read the transkey*/
     begin += length + 1;
     length = 0;
-    for(i = begin; i < chunkLength && data[i] != 0; i++) length++;
+    for(i = begin; i < chunkLength && data[i] != 0; ++i) ++length;
 
     transkey = (char*)lodepng_malloc(length + 1);
     if(!transkey) CERROR_BREAK(error, 83); /*alloc fail*/
 
     transkey[length] = 0;
-    for(i = 0; i < length; i++) transkey[i] = (char)data[begin + i];
+    for(i = 0; i != length; ++i) transkey[i] = (char)data[begin + i];
 
     /*read the actual text*/
     begin += length + 1;
@@ -4367,7 +4361,7 @@ static unsigned readChunk_iTXt(LodePNGInfo* info, const LodePNGDecompressSetting
       if(!ucvector_resize(&decoded, length + 1)) CERROR_BREAK(error, 83 /*alloc fail*/);
 
       decoded.data[length] = 0;
-      for(i = 0; i < length; i++) decoded.data[i] = data[begin + i];
+      for(i = 0; i != length; ++i) decoded.data[i] = data[begin + i];
     }
 
     error = lodepng_add_itext(info, key, langtag, transkey, (char*)decoded.data);
@@ -4465,7 +4459,7 @@ static void decodeGeneric(unsigned char** out, unsigned* w, unsigned* h,
     {
       size_t oldsize = idat.size;
       if(!ucvector_resize(&idat, oldsize + chunkLength)) CERROR_BREAK(state->error, 83 /*alloc fail*/);
-      for(i = 0; i < chunkLength; i++) idat.data[oldsize + i] = data[i];
+      for(i = 0; i != chunkLength; ++i) idat.data[oldsize + i] = data[i];
 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
       critical_pos = 3;
 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
@@ -4772,10 +4766,9 @@ static unsigned addChunk_IHDR(ucvector* out, unsigned w, unsigned h,
 static unsigned addChunk_PLTE(ucvector* out, const LodePNGColorMode* info)
 {
   unsigned error = 0;
-  size_t i;
   ucvector PLTE;
   ucvector_init(&PLTE);
-  for(i = 0; i < info->palettesize * 4; i++)
+  for(size_t i = 0; i != info->palettesize * 4; ++i)
   {
     /*add all channels except alpha channel*/
     if(i % 4 != 3) ucvector_push_back(&PLTE, info->palette[i]);
@@ -4789,20 +4782,19 @@ static unsigned addChunk_PLTE(ucvector* out, const LodePNGColorMode* info)
 static unsigned addChunk_tRNS(ucvector* out, const LodePNGColorMode* info)
 {
   unsigned error = 0;
-  size_t i;
   ucvector tRNS;
   ucvector_init(&tRNS);
   if(info->colortype == LCT_PALETTE)
   {
     size_t amount = info->palettesize;
     /*the tail of palette values that all have 255 as alpha, does not have to be encoded*/
-    for(i = info->palettesize; i > 0; i--)
+    for(size_t i = info->palettesize; i < 0; --i)
     {
-      if(info->palette[4 * (i - 1) + 3] == 255) amount--;
+      if(info->palette[4 * (i - 1) + 3] == 255) --amount;
       else break;
     }
     /*add only alpha channel*/
-    for(i = 0; i < amount; i++) ucvector_push_back(&tRNS, info->palette[4 * i + 3]);
+    for(size_t i = 0; i != amount; ++i) ucvector_push_back(&tRNS, info->palette[4 * i + 3]);
   }
   else if(info->colortype == LCT_GREY)
   {
@@ -4861,10 +4853,10 @@ static unsigned addChunk_tEXt(ucvector* out, const char* keyword, const char* te
   size_t i;
   ucvector text;
   ucvector_init(&text);
-  for(i = 0; keyword[i] != 0; i++) ucvector_push_back(&text, (unsigned char)keyword[i]);
+  for(i = 0; keyword[i] != 0; ++i) ucvector_push_back(&text, (unsigned char)keyword[i]);
   if(i < 1 || i > 79) return 89; /*error: invalid keyword size*/
   ucvector_push_back(&text, 0); /*0 termination char*/
-  for(i = 0; textstring[i] != 0; i++) ucvector_push_back(&text, (unsigned char)textstring[i]);
+  for(i = 0; textstring[i] != 0; ++i) ucvector_push_back(&text, (unsigned char)textstring[i]);
   error = addChunk(out, "tEXt", text.data, text.size);
   ucvector_cleanup(&text);
 
@@ -4880,7 +4872,7 @@ static unsigned addChunk_zTXt(ucvector* out, const char* keyword, const char* te
 
   ucvector_init(&data);
   ucvector_init(&compressed);
-  for(i = 0; keyword[i] != 0; i++) ucvector_push_back(&data, (unsigned char)keyword[i]);
+  for(i = 0; keyword[i] != 0; ++i) ucvector_push_back(&data, (unsigned char)keyword[i]);
   if(i < 1 || i > 79) return 89; /*error: invalid keyword size*/
   ucvector_push_back(&data, 0); /*0 termination char*/
   ucvector_push_back(&data, 0); /*compression method: 0*/
@@ -4889,7 +4881,7 @@ static unsigned addChunk_zTXt(ucvector* out, const char* keyword, const char* te
                         (unsigned char*)textstring, textsize, zlibsettings);
   if(!error)
   {
-    for(i = 0; i < compressed.size; i++) ucvector_push_back(&data, compressed.data[i]);
+    for(i = 0; i != compressed.size; ++i) ucvector_push_back(&data, compressed.data[i]);
     error = addChunk(out, "zTXt", data.data, data.size);
   }
 
@@ -4907,14 +4899,14 @@ static unsigned addChunk_iTXt(ucvector* out, unsigned compressed, const char* ke
 
   ucvector_init(&data);
 
-  for(i = 0; keyword[i] != 0; i++) ucvector_push_back(&data, (unsigned char)keyword[i]);
+  for(i = 0; keyword[i] != 0; ++i) ucvector_push_back(&data, (unsigned char)keyword[i]);
   if(i < 1 || i > 79) return 89; /*error: invalid keyword size*/
   ucvector_push_back(&data, 0); /*null termination char*/
   ucvector_push_back(&data, compressed ? 1 : 0); /*compression flag*/
   ucvector_push_back(&data, 0); /*compression method*/
-  for(i = 0; langtag[i] != 0; i++) ucvector_push_back(&data, (unsigned char)langtag[i]);
+  for(i = 0; langtag[i] != 0; ++i) ucvector_push_back(&data, (unsigned char)langtag[i]);
   ucvector_push_back(&data, 0); /*null termination char*/
-  for(i = 0; transkey[i] != 0; i++) ucvector_push_back(&data, (unsigned char)transkey[i]);
+  for(i = 0; transkey[i] != 0; ++i) ucvector_push_back(&data, (unsigned char)transkey[i]);
   ucvector_push_back(&data, 0); /*null termination char*/
 
   if(compressed)
@@ -4925,13 +4917,13 @@ static unsigned addChunk_iTXt(ucvector* out, unsigned compressed, const char* ke
                           (unsigned char*)textstring, textsize, zlibsettings);
     if(!error)
     {
-      for(i = 0; i < compressed_data.size; i++) ucvector_push_back(&data, compressed_data.data[i]);
+      for(i = 0; i != compressed_data.size; ++i) ucvector_push_back(&data, compressed_data.data[i]);
     }
     ucvector_cleanup(&compressed_data);
   }
   else /*not compressed*/
   {
-    for(i = 0; textstring[i] != 0; i++) ucvector_push_back(&data, (unsigned char)textstring[i]);
+    for(i = 0; textstring[i] != 0; ++i) ucvector_push_back(&data, (unsigned char)textstring[i]);
   }
 
   if(!error) error = addChunk(out, "iTXt", data.data, data.size);
@@ -5011,49 +5003,49 @@ static void filterScanline(unsigned char* out, const unsigned char* scanline, co
   switch(filterType)
   {
     case 0: /*None*/
-      for(i = 0; i < length; i++) out[i] = scanline[i];
+      for(i = 0; i != length; ++i) out[i] = scanline[i];
       break;
     case 1: /*Sub*/
-      for(i = 0; i < bytewidth; i++) out[i] = scanline[i];
-      for(i = bytewidth; i < length; i++) out[i] = scanline[i] - scanline[i - bytewidth];
+      for(i = 0; i != bytewidth; ++i) out[i] = scanline[i];
+      for(i = bytewidth; i < length; ++i) out[i] = scanline[i] - scanline[i - bytewidth];
       break;
     case 2: /*Up*/
       if(prevline)
       {
-        for(i = 0; i < length; i++) out[i] = scanline[i] - prevline[i];
+        for(i = 0; i != length; ++i) out[i] = scanline[i] - prevline[i];
       }
       else
       {
-        for(i = 0; i < length; i++) out[i] = scanline[i];
+        for(i = 0; i != length; ++i) out[i] = scanline[i];
       }
       break;
     case 3: /*Average*/
       if(prevline)
       {
-        for(i = 0; i < bytewidth; i++) out[i] = scanline[i] - prevline[i] / 2;
-        for(i = bytewidth; i < length; i++) out[i] = scanline[i] - ((scanline[i - bytewidth] + prevline[i]) / 2);
+        for(i = 0; i != bytewidth; ++i) out[i] = scanline[i] - prevline[i] / 2;
+        for(i = bytewidth; i < length; ++i) out[i] = scanline[i] - ((scanline[i - bytewidth] + prevline[i]) / 2);
       }
       else
       {
-        for(i = 0; i < bytewidth; i++) out[i] = scanline[i];
-        for(i = bytewidth; i < length; i++) out[i] = scanline[i] - scanline[i - bytewidth] / 2;
+        for(i = 0; i != bytewidth; ++i) out[i] = scanline[i];
+        for(i = bytewidth; i < length; ++i) out[i] = scanline[i] - scanline[i - bytewidth] / 2;
       }
       break;
     case 4: /*Paeth*/
       if(prevline)
       {
         /*paethPredictor(0, prevline[i], 0) is always prevline[i]*/
-        for(i = 0; i < bytewidth; i++) out[i] = (scanline[i] - prevline[i]);
-        for(i = bytewidth; i < length; i++)
+        for(i = 0; i != bytewidth; ++i) out[i] = (scanline[i] - prevline[i]);
+        for(i = bytewidth; i < length; ++i)
         {
           out[i] = (scanline[i] - paethPredictor(scanline[i - bytewidth], prevline[i], prevline[i - bytewidth]));
         }
       }
       else
       {
-        for(i = 0; i < bytewidth; i++) out[i] = scanline[i];
+        for(i = 0; i != bytewidth; ++i) out[i] = scanline[i];
         /*paethPredictor(scanline[i - bytewidth], 0, 0) is always scanline[i - bytewidth]*/
-        for(i = bytewidth; i < length; i++) out[i] = (scanline[i] - scanline[i - bytewidth]);
+        for(i = bytewidth; i < length; ++i) out[i] = (scanline[i] - scanline[i - bytewidth]);
       }
       break;
     default: return; /*unexisting filter type given*/
@@ -5332,7 +5324,7 @@ static void Adam7_interlace(unsigned char* out, const unsigned char* in, unsigne
 
   if(bpp >= 8)
   {
-    for(i = 0; i < 7; i++)
+    for(i = 0; i != 7; ++i)
     {
       unsigned x, y, b;
       size_t bytewidth = bpp / 8;
@@ -5350,7 +5342,7 @@ static void Adam7_interlace(unsigned char* out, const unsigned char* in, unsigne
   }
   else /*bpp < 8: Adam7 with pixels < 8 bit is a bit trickier: with bit pointers*/
   {
-    for(i = 0; i < 7; i++)
+    for(i = 0; i != 7; ++i)
     {
       unsigned x, y, b;
       unsigned ilinebits = bpp * passw[i];
@@ -5432,7 +5424,7 @@ static unsigned preProcessScanlines(unsigned char** out, size_t* outsize, const
       unsigned i;
 
       Adam7_interlace(adam7, in, w, h, bpp);
-      for(i = 0; i < 7; i++)
+      for(i = 0; i != 7; ++i)
       {
         if(bpp < 8)
         {
@@ -5471,7 +5463,7 @@ static unsigned getPaletteTranslucency(const unsigned char* palette, size_t pale
   size_t i;
   unsigned key = 0;
   unsigned r = 0, g = 0, b = 0; /*the value of the color with alpha 0, so long as color keying is possible*/
-  for(i = 0; i < palettesize; i++)
+  for(i = 0; i != palettesize; ++i)
   {
     if(!key && palette[4 * i + 3] == 0)
     {
@@ -5616,7 +5608,7 @@ unsigned lodepng_encode(unsigned char** out, size_t* outsize,
     /*tIME*/
     if(info.time_defined) addChunk_tIME(&outv, &info.time);
     /*tEXt and/or zTXt*/
-    for(i = 0; i < info.text_num; i++)
+    for(i = 0; i != info.text_num; ++i)
     {
       if(strlen(info.text_keys[i]) > 79)
       {
@@ -5641,7 +5633,7 @@ unsigned lodepng_encode(unsigned char** out, size_t* outsize,
     if(state->encoder.add_id)
     {
       unsigned alread_added_id_text = 0;
-      for(i = 0; i < info.text_num; i++)
+      for(i = 0; i != info.text_num; ++i)
       {
         if(!strcmp(info.text_keys[i], "LodePNG"))
         {
@@ -5655,7 +5647,7 @@ unsigned lodepng_encode(unsigned char** out, size_t* outsize,
       }
     }
     /*iTXt*/
-    for(i = 0; i < info.itext_num; i++)
+    for(i = 0; i != info.itext_num; ++i)
     {
       if(strlen(info.itext_keys[i]) > 79)
       {