third_party/libwebp/utils/utils.h

   1 // Copyright 2012 Google Inc. All Rights Reserved.
   2 //
   3 // Use of this source code is governed by a BSD-style license
   4 // that can be found in the COPYING file in the root of the source
   5 // tree. An additional intellectual property rights grant can be found
   6 // in the file PATENTS. All contributing project authors may
   7 // be found in the AUTHORS file in the root of the source tree.
   8 // -----------------------------------------------------------------------------
   9 //
  10 // Misc. common utility functions
  11 //
  12 // Authors: Skal (pascal.massimino@gmail.com)
  13 //          Urvang (urvang@google.com)
  14
  15 #ifndef WEBP_UTILS_UTILS_H_
  16 #define WEBP_UTILS_UTILS_H_
  17
  18 #include <assert.h>
  19
  20 #include "../webp/types.h"
  21
  22 #ifdef __cplusplus
  23 extern "C" {
  24 #endif
  25
  26 //------------------------------------------------------------------------------
  27 // Memory allocation
  28
  29 // This is the maximum memory amount that libwebp will ever try to allocate.
  30 #define WEBP_MAX_ALLOCABLE_MEMORY (1ULL << 40)
  31
  32 // size-checking safe malloc/calloc: verify that the requested size is not too
  33 // large, or return NULL. You don't need to call these for constructs like
  34 // malloc(sizeof(foo)), but only if there's picture-dependent size involved
  35 // somewhere (like: malloc(num_pixels * sizeof(*something))). That's why this
  36 // safe malloc() borrows the signature from calloc(), pointing at the dangerous
  37 // underlying multiply involved.
  38 WEBP_EXTERN(void*) WebPSafeMalloc(uint64_t nmemb, size_t size);
  39 // Note that WebPSafeCalloc() expects the second argument type to be 'size_t'
  40 // in order to favor the "calloc(num_foo, sizeof(foo))" pattern.
  41 WEBP_EXTERN(void*) WebPSafeCalloc(uint64_t nmemb, size_t size);
  42
  43 // Companion deallocation function to the above allocations.
  44 WEBP_EXTERN(void) WebPSafeFree(void* const ptr);
  45
  46 //------------------------------------------------------------------------------
  47 // Reading/writing data.
  48
  49 // Read 16, 24 or 32 bits stored in little-endian order.
  50 static WEBP_INLINE int GetLE16(const uint8_t* const data) {
  51   return (int)(data[0] << 0) | (data[1] << 8);
  52 }
  53
  54 static WEBP_INLINE int GetLE24(const uint8_t* const data) {
  55   return GetLE16(data) | (data[2] << 16);
  56 }
  57
  58 static WEBP_INLINE uint32_t GetLE32(const uint8_t* const data) {
  59   return (uint32_t)GetLE16(data) | (GetLE16(data + 2) << 16);
  60 }
  61
  62 // Store 16, 24 or 32 bits in little-endian order.
  63 static WEBP_INLINE void PutLE16(uint8_t* const data, int val) {
  64   assert(val < (1 << 16));
  65   data[0] = (val >> 0);
  66   data[1] = (val >> 8);
  67 }
  68
  69 static WEBP_INLINE void PutLE24(uint8_t* const data, int val) {
  70   assert(val < (1 << 24));
  71   PutLE16(data, val & 0xffff);
  72   data[2] = (val >> 16);
  73 }
  74
  75 static WEBP_INLINE void PutLE32(uint8_t* const data, uint32_t val) {
  76   PutLE16(data, (int)(val & 0xffff));
  77   PutLE16(data + 2, (int)(val >> 16));
  78 }
  79
  80 // Returns (int)floor(log2(n)). n must be > 0.
  81 // use GNU builtins where available.
  82 #if defined(__GNUC__) && \
  83     ((__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || __GNUC__ >= 4)
  84 static WEBP_INLINE int BitsLog2Floor(uint32_t n) {
  85   return 31 ^ __builtin_clz(n);
  86 }
  87 #elif defined(_MSC_VER) && _MSC_VER > 1310 && \
  88       (defined(_M_X64) || defined(_M_IX86))
  89 #include <intrin.h>
  90 #pragma intrinsic(_BitScanReverse)
  91
  92 static WEBP_INLINE int BitsLog2Floor(uint32_t n) {
  93   unsigned long first_set_bit;
  94   _BitScanReverse(&first_set_bit, n);
  95   return first_set_bit;
  96 }
  97 #else
  98 static WEBP_INLINE int BitsLog2Floor(uint32_t n) {
  99   int log = 0;
 100   uint32_t value = n;
 101   int i;
 102
 103   for (i = 4; i >= 0; --i) {
 104     const int shift = (1 << i);
 105     const uint32_t x = value >> shift;
 106     if (x != 0) {
 107       value = x;
 108       log += shift;
 109     }
 110   }
 111   return log;
 112 }
 113 #endif
 114
 115 //------------------------------------------------------------------------------
 116
 117 #ifdef __cplusplus
 118 }    // extern "C"
 119 #endif
 120
 121 #endif  /* WEBP_UTILS_UTILS_H_ */