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
23extern "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.
38WEBP_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.
41WEBP_EXTERN(void*) WebPSafeCalloc(uint64_t nmemb, size_t size);
42
43// Companion deallocation function to the above allocations.
44WEBP_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.
50static WEBP_INLINE int GetLE16(const uint8_t* const data) {
51  return (int)(data[0] << 0) | (data[1] << 8);
52}
53
54static WEBP_INLINE int GetLE24(const uint8_t* const data) {
55  return GetLE16(data) | (data[2] << 16);
56}
57
58static 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.
63static 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
69static 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
75static 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)
84static 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
92static WEBP_INLINE int BitsLog2Floor(uint32_t n) {
93  uint32_t first_set_bit;
94  _BitScanReverse(&first_set_bit, n);
95  return first_set_bit;
96}
97#else
98static 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_ */
122