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Deduct identical byte count from compressed size

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Aetias
2023-09-21 23:02:07 +02:00
parent 277a4d6e3d
commit 55ae38a147
1 changed files with 19 additions and 6 deletions
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tools/compress/main.c
+19 -6
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@@ -54,14 +54,25 @@ bool FindSubsequence(const uint8_t *buf, const uint8_t *start, const uint8_t *en
return true;
}
bool Compress(const uint8_t *src, uint8_t *dst, size_t size, uint8_t **pResult, size_t *pLen) {
bool Compress(const uint8_t *src, uint8_t *dst, size_t size, uint8_t **pResult, size_t *pLen, size_t *pNumIdentical) {
const uint8_t *end = src + size;
const uint8_t *read = end;
uint8_t *write = dst + size - 1;
uint8_t *writeEnd = dst + size;
uint8_t *write = writeEnd - 1;
uint8_t *pFlags = write;
uint8_t flags;
size_t flagCount = 0;
size_t numIdentical = 0;
while (read > src) {
if (read - 1 == src && flagCount == 0) {
read -= 1;
*write = *read;
for (numIdentical = 0; write + numIdentical < writeEnd; ++numIdentical) {
if (read[numIdentical] != write[numIdentical]) break;
}
write -= 1;
break;
}
flags <<= 1;
size_t len, dist;
if (FindSubsequence(read - 1, src, end, &len, &dist)) {
@@ -90,16 +101,18 @@ bool Compress(const uint8_t *src, uint8_t *dst, size_t size, uint8_t **pResult,
else write += 1;
*pResult = write;
*pLen = size - (write - dst);
*pNumIdentical = numIdentical;
return true;
}
bool WriteFooter(FILE *fp, const char *fileName, bool addPadding, uint32_t compressedSize, uint32_t originalSize, uint32_t start) {
bool WriteFooter(FILE *fp, const char *fileName, bool addPadding, uint32_t compressedSize, uint32_t originalSize, uint32_t start, uint32_t numIdentical) {
size_t padding = 0;
if (addPadding) padding = (0x4 - (compressedSize & 0x3)) & 0x3;
for (size_t i = 0; i < padding; ++i) fputc(0xFF, fp);
compressedSize += padding + 8;
uint32_t readOffset = padding + 8;
uint32_t writeOffset = originalSize - compressedSize - start;
compressedSize -= numIdentical;
if (fwrite(&compressedSize, 3, 1, fp) != 1) {
if (fp == stdout) fprintf(stderr, "Failed to write compressed size to stdout\n");
else fprintf(stderr, "Failed to write compressed size to '%s'\n", fileName);
@@ -211,14 +224,14 @@ int main(int argc, const char **argv) {
uint8_t *outBuf = malloc(inSize - start);
uint8_t *result;
size_t resultLen;
if (!Compress(buf + start, outBuf, inSize - start, &result, &resultLen)) return 1;
size_t resultLen, numIdentical;
if (!Compress(buf + start, outBuf, inSize - start, &result, &resultLen, &numIdentical)) return 1;
if (fwrite(result, resultLen, 1, fpIn) != 1) {
if (fpOut == stdout) fprintf(stderr, "Failed to write compressed output to stdout\n");
else fprintf(stderr, "Failed to write compressed output to '%s'\n", outFile);
return 1;
}
if (!WriteFooter(fpOut, outFile, padCompressedBlock, resultLen, inSize, start)) return 1;
if (!WriteFooter(fpOut, outFile, padCompressedBlock, resultLen, inSize, start, numIdentical)) return 1;
free(outBuf);
if (outFile != NULL) fclose(fpOut);