Remove unused PackBits methods and fix length checks

src/core/SkPackBits.cpp

-
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkPackBits.h"
 
-#define GATHER_STATSx
-
-static inline void small_memcpy(void* SK_RESTRICT dst,
-                                const void* SK_RESTRICT src, size_t n) {
-    SkASSERT(n > 0 && n <= 15);
-    uint8_t* d = (uint8_t*)dst;
-    const uint8_t* s = (const uint8_t*)src;
-    switch (n) {
-        case 15: *d++ = *s++;
-        case 14: *d++ = *s++;
-        case 13: *d++ = *s++;
-        case 12: *d++ = *s++;
-        case 11: *d++ = *s++;
-        case 10: *d++ = *s++;
-        case  9: *d++ = *s++;
-        case  8: *d++ = *s++;
-        case  7: *d++ = *s++;
-        case  6: *d++ = *s++;
-        case  5: *d++ = *s++;
-        case  4: *d++ = *s++;
-        case  3: *d++ = *s++;
-        case  2: *d++ = *s++;
-        case  1: *d++ = *s++;
-        case  0: break;
-    }
-}
-
-static inline void small_memset(void* dst, uint8_t value, size_t n) {
-    SkASSERT(n > 0 && n <= 15);
-    uint8_t* d = (uint8_t*)dst;
-    switch (n) {
-        case 15: *d++ = value;
-        case 14: *d++ = value;
-        case 13: *d++ = value;
-        case 12: *d++ = value;
-        case 11: *d++ = value;
-        case 10: *d++ = value;
-        case  9: *d++ = value;
-        case  8: *d++ = value;
-        case  7: *d++ = value;
-        case  6: *d++ = value;
-        case  5: *d++ = value;
-        case  4: *d++ = value;
-        case  3: *d++ = value;
-        case  2: *d++ = value;
-        case  1: *d++ = value;
-        case  0: break;
-    }
-}
-
-// can we do better for small counts with our own inlined memcpy/memset?
-
-#define PB_MEMSET(addr, value, count)       \
-do {                                        \
-if ((count) > 15) {                     \
-memset(addr, value, count);         \
-} else {                                \
-small_memset(addr, value, count);   \
-}                                       \
-} while (0)
-
-#define PB_MEMCPY(dst, src, count)      \
-do {                                    \
-    if ((count) > 15) {                 \
-        memcpy(dst, src, count);        \
-    } else {                            \
-        small_memcpy(dst, src, count);  \
-    }                                   \
-} while (0)
-
-///////////////////////////////////////////////////////////////////////////////
-
-#ifdef GATHER_STATS
-    static int gMemSetBuckets[129];
-    static int gMemCpyBuckets[129];
-    static int gCounter;
-
-static void register_memset_count(int n) {
-    SkASSERT((unsigned)n <= 128);
-    gMemSetBuckets[n] += 1;
-    gCounter += 1;
-
-    if ((gCounter & 0xFF) == 0) {
-        SkDebugf("----- packbits memset stats: ");
-        for (size_t i = 0; i < SK_ARRAY_COUNT(gMemSetBuckets); i++) {
-            if (gMemSetBuckets[i]) {
-                SkDebugf(" %d:%d", i, gMemSetBuckets[i]);
-            }
-        }
-    }
-}
-static void register_memcpy_count(int n) {
-    SkASSERT((unsigned)n <= 128);
-    gMemCpyBuckets[n] += 1;
-    gCounter += 1;
-
-    if ((gCounter & 0x1FF) == 0) {
-        SkDebugf("----- packbits memcpy stats: ");
-        for (size_t i = 0; i < SK_ARRAY_COUNT(gMemCpyBuckets); i++) {
-            if (gMemCpyBuckets[i]) {
-                SkDebugf(" %d:%d", i, gMemCpyBuckets[i]);
-            }
-        }
-    }
-}
-#else
-#define register_memset_count(n)
-#define register_memcpy_count(n)
-#endif
-
-
-///////////////////////////////////////////////////////////////////////////////
-
-size_t SkPackBits::ComputeMaxSize16(int count) {
-    // worst case is the number of 16bit values (times 2) +
-    // 1 byte per (up to) 128 entries.
-    return ((count + 127) >> 7) + (count << 1);
-}
-
 size_t SkPackBits::ComputeMaxSize8(int count) {
     // worst case is the number of 8bit values + 1 byte per (up to) 128 entries.
     return ((count + 127) >> 7) + count;
 }
 
-static uint8_t* flush_same16(uint8_t dst[], uint16_t value, int count) {
+static uint8_t* flush_same8(uint8_t dst[], uint8_t value, size_t count) {
     while (count > 0) {
-        int n = count;
-        if (n > 128) {
-            n = 128;
-        }
-        *dst++ = (uint8_t)(n - 1);
-        *dst++ = (uint8_t)(value >> 8);
-        *dst++ = (uint8_t)value;
-        count -= n;
-    }
-    return dst;
-}
-
-static uint8_t* flush_same8(uint8_t dst[], uint8_t value, int count) {
-    while (count > 0) {
-        int n = count;
-        if (n > 128) {
-            n = 128;
-        }
+        int n = count > 128 ? 128 : count;
         *dst++ = (uint8_t)(n - 1);
         *dst++ = (uint8_t)value;
         count -= n;
     }
     return dst;
 }
 
-static uint8_t* flush_diff16(uint8_t* SK_RESTRICT dst,
-                             const uint16_t* SK_RESTRICT src, int count) {
+static uint8_t* flush_diff8(uint8_t* SK_RESTRICT dst,
+                            const uint8_t* SK_RESTRICT src, size_t count) {
     while (count > 0) {
-        int n = count;
-        if (n > 128) {
-            n = 128;
-        }
+        int n = count > 128 ? 128 : count;
         *dst++ = (uint8_t)(n + 127);
-        PB_MEMCPY(dst, src, n * sizeof(uint16_t));
-        src += n;
-        dst += n * sizeof(uint16_t);
-        count -= n;
-    }
-    return dst;
-}
-
-static uint8_t* flush_diff8(uint8_t* SK_RESTRICT dst,
-                            const uint8_t* SK_RESTRICT src, int count) {
-    while (count > 0) {
-        int n = count;
-        if (n > 128) {
-            n = 128;
-        }
-        *dst++ = (uint8_t)(n + 127);
-        PB_MEMCPY(dst, src, n);
+        memcpy(dst, src, n);
         src += n;
         dst += n;
         count -= n;
     }
     return dst;
 }
 
-size_t SkPackBits::Pack16(const uint16_t* SK_RESTRICT src, int count,
-                          uint8_t* SK_RESTRICT dst) {
-    uint8_t* origDst = dst;
-    const uint16_t* stop = src + count;
+size_t SkPackBits::Pack8(const uint8_t* SK_RESTRICT src, size_t srcSize,
+                         uint8_t* SK_RESTRICT dst, size_t dstSize) {
+    if (dstSize < ComputeMaxSize8(srcSize)) {
+        return 0;
+    }
 
-    for (;;) {
-        count = SkToInt(stop - src);
-        SkASSERT(count >= 0);
-        if (count == 0) {
-            return dst - origDst;
-        }
+    uint8_t* const origDst = dst;
+    const uint8_t* stop = src + srcSize;
+
+    for (intptr_t count = stop - src; count > 0; count = stop - src) {
         if (1 == count) {
             *dst++ = 0;
-            *dst++ = (uint8_t)(*src >> 8);
-            *dst++ = (uint8_t)*src;
-            return dst - origDst;
+            *dst++ = *src;
+            break;
         }
 
         unsigned value = *src;
-        const uint16_t* s = src + 1;
-
-        if (*s == value) { // accumulate same values...
-            do {
-                s++;
-                if (s == stop) {
-                    break;
-                }
-            } while (*s == value);
-            dst = flush_same16(dst, value, SkToInt(s - src));
-        } else {    // accumulate diff values...
-            do {
-                if (++s == stop) {
-                    goto FLUSH_DIFF;
-                }
-            } while (*s != s[-1]);
-            s -= 1; // back up so we don't grab one of the "same" values that follow
-        FLUSH_DIFF:
-            dst = flush_diff16(dst, src, SkToInt(s - src));
-        }
-        src = s;
-    }
-}
-
-size_t SkPackBits::Pack8(const uint8_t* SK_RESTRICT src, int count,
-                         uint8_t* SK_RESTRICT dst) {
-    uint8_t* origDst = dst;
-    const uint8_t* stop = src + count;
-
-    for (;;) {
-        count = SkToInt(stop - src);
-        SkASSERT(count >= 0);
-        if (count == 0) {
-            return dst - origDst;
-        }
-        if (1 == count) {
-            *dst++ = 0;
-            *dst++ = *src;
-            return dst - origDst;
-        }
-
-        unsigned value = *src;
         const uint8_t* s = src + 1;
 
         if (*s == value) { // accumulate same values...
             do {
                 s++;
                 if (s == stop) {
                     break;
                 }
             } while (*s == value);
             dst = flush_same8(dst, value, SkToInt(s - src));
         } else {    // accumulate diff values...
             do {
                 if (++s == stop) {
                     goto FLUSH_DIFF;
                 }
                 // only stop if we hit 3 in a row,
                 // otherwise we get bigger than compuatemax
             } while (*s != s[-1] || s[-1] != s[-2]);
             s -= 2; // back up so we don't grab the "same" values that follow
         FLUSH_DIFF:
             dst = flush_diff8(dst, src, SkToInt(s - src));
         }
         src = s;
     }
+    return dst - origDst;
 }
 
 #include "SkUtils.h"
 
-int SkPackBits::Unpack16(const uint8_t* SK_RESTRICT src, size_t srcSize,
-                         uint16_t* SK_RESTRICT dst) {
-    uint16_t* origDst = dst;
+int SkPackBits::Unpack8(const uint8_t* SK_RESTRICT src, size_t srcSize,
+                        uint8_t* SK_RESTRICT dst, size_t dstSize) {
+    uint8_t* const origDst = dst;
+    uint8_t* const endDst = dst + dstSize;
     const uint8_t* stop = src + srcSize;
 
     while (src < stop) {
         unsigned n = *src++;
         if (n <= 127) {   // repeat count (n + 1)
             n += 1;
-            sk_memset16(dst, (src[0] << 8) | src[1], n);
-            src += 2;
+            if (dst >(endDst - n)) {
+                return 0;
+            }
+            memset(dst, *src++, n);
         } else {    // same count (n - 127)
             n -= 127;
-            PB_MEMCPY(dst, src, n * sizeof(uint16_t));
-            src += n * sizeof(uint16_t);
-        }
-        dst += n;
-    }
-    SkASSERT(src == stop);
-    return SkToInt(dst - origDst);
-}
-
-int SkPackBits::Unpack8(const uint8_t* SK_RESTRICT src, size_t srcSize,
-                        uint8_t* SK_RESTRICT dst) {
-    uint8_t* origDst = dst;
-    const uint8_t* stop = src + srcSize;
-
-    while (src < stop) {
-        unsigned n = *src++;
-        if (n <= 127) {   // repeat count (n + 1)
-            n += 1;
-            PB_MEMSET(dst, *src++, n);
-        } else {    // same count (n - 127)
-            n -= 127;
-            PB_MEMCPY(dst, src, n);
+            if (dst > (endDst - n)) {
+                return 0;
+            }
+            memcpy(dst, src, n);
             src += n;
         }
         dst += n;
     }
-    SkASSERT(src == stop);
+    SkASSERT(src <= stop);
     return SkToInt(dst - origDst);
 }
-
-enum UnpackState {
-    CLEAN_STATE,
-    REPEAT_BYTE_STATE,
-    COPY_SRC_STATE
-};
-
-void SkPackBits::Unpack8(uint8_t* SK_RESTRICT dst, size_t dstSkip,
-                         size_t dstWrite, const uint8_t* SK_RESTRICT src) {
-    if (dstWrite == 0) {
-        return;
-    }
-
-    UnpackState state = CLEAN_STATE;
-    size_t      stateCount = 0;
-
-    // state 1: do the skip-loop
-    while (dstSkip > 0) {
-        size_t n = *src++;
-        if (n <= 127) {   // repeat count (n + 1)
-            n += 1;
-            if (n > dstSkip) {
-                state = REPEAT_BYTE_STATE;
-                stateCount = n - dstSkip;
-                n = dstSkip;
-                // we don't increment src here, since its needed in stage 2
-            } else {
-                src++;  // skip the src byte
-            }
-        } else {    // same count (n - 127)
-            n -= 127;
-            if (n > dstSkip) {
-                state = COPY_SRC_STATE;
-                stateCount = n - dstSkip;
-                n = dstSkip;
-            }
-            src += n;
-        }
-        dstSkip -= n;
-    }
-
-    // stage 2: perform any catchup from the skip-stage
-    if (stateCount > dstWrite) {
-        stateCount = dstWrite;
-    }
-    switch (state) {
-        case REPEAT_BYTE_STATE:
-            SkASSERT(stateCount > 0);
-            register_memset_count(stateCount);
-            PB_MEMSET(dst, *src++, stateCount);
-            break;
-        case COPY_SRC_STATE:
-            SkASSERT(stateCount > 0);
-            register_memcpy_count(stateCount);
-            PB_MEMCPY(dst, src, stateCount);
-            src += stateCount;
-            break;
-        default:
-            SkASSERT(stateCount == 0);
-            break;
-    }
-    dst += stateCount;
-    dstWrite -= stateCount;
-
-    // copy at most dstWrite bytes into dst[]
-    while (dstWrite > 0) {
-        size_t n = *src++;
-        if (n <= 127) {   // repeat count (n + 1)
-            n += 1;
-            if (n > dstWrite) {
-                n = dstWrite;
-            }
-            register_memset_count(n);
-            PB_MEMSET(dst, *src++, n);
-        } else {    // same count (n - 127)
-            n -= 127;
-            if (n > dstWrite) {
-                n = dstWrite;
-            }
-            register_memcpy_count(n);
-            PB_MEMCPY(dst, src, n);
-            src += n;
-        }
-        dst += n;
-        dstWrite -= n;
-    }
-    SkASSERT(0 == dstWrite);
-}