mirror of https://github.com/fadden/fhpack.git
Fix bug in compression code
In some situations, a run of exactly 15 literals would be encoded incorrectly.
This commit is contained in:
Andy McFadden
parent
edd69c37d2
commit
90069ef14e
29
fhpack.cpp
29
fhpack.cpp
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@ -1,7 +1,7 @@
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/*
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* fhpack, an Apple II hi-res picture compressor.
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* By Andy McFadden
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* Version 1.0, August 2015
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* Version 1.0.1, August 2023
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*
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* Copyright 2015 by faddenSoft. All Rights Reserved.
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* See the LICENSE.txt file for distribution terms (Apache 2.0).
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@ -88,7 +88,6 @@ every 255 literals (4/4 byte, 1 for literal len extension, 1 for match
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len extension that holds the "no match" symbol). Globally we add +1 for
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the magic number. The "end-of-data" symbol replaces the "no match"
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symbol, so overall it's int(ceil(8192/255)) * 33 + 1 = 100 bytes.
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*/
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/*
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Implementation notes:
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@ -158,7 +157,7 @@ enum ProgramMode {
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*/
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static void usage(const char* argv0)
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{
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fprintf(stderr, "fhpack v1.0 by Andy McFadden -*- ");
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fprintf(stderr, "fhpack v1.0.1 by Andy McFadden -*- ");
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fprintf(stderr, "Copyright 2015 by faddenSoft\n");
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fprintf(stderr,
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"Source code available from https://github.com/fadden/fhpack\n\n");
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@ -447,9 +446,11 @@ size_t compressBufferOptimally(uint8_t* outBuf, const uint8_t* inBuf,
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// backwards, we can end up with 32 literals followed
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// by 255 literals, rather than the other way around.
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DBUG((" output literal-literal (%zd)\n", numLiterals));
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if (numLiterals <= INITIAL_LEN) {
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if (numLiterals < INITIAL_LEN) {
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// output 0-14 literals
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*outPtr++ = (numLiterals << 4) | 0x0f;
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} else {
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// output 15+(0-240) literals
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*outPtr++ = 0xff;
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*outPtr++ = numLiterals - INITIAL_LEN;
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}
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@ -513,9 +514,12 @@ size_t compressBufferOptimally(uint8_t* outBuf, const uint8_t* inBuf,
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// Dump any remaining literals, with the end-of-data indicator
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// in the match len.
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if (numLiterals <= INITIAL_LEN) {
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DBUG(("ending with numLiterals=%zd\n", numLiterals));
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if (numLiterals < INITIAL_LEN) {
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// 0-14 literals, only need the nibble
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*outPtr++ = (numLiterals << 4) | 0x0f;
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} else {
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// 15-255 literals, need the extra byte
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*outPtr++ = 0xff;
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*outPtr++ = numLiterals - INITIAL_LEN;
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}
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@ -570,7 +574,7 @@ size_t compressBufferGreedily(uint8_t* outBuf, const uint8_t* inBuf,
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if (numLiterals == MAX_LITERAL_LEN) {
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// We've maxed out the literal string length. Emit
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// the previously literals with an empty match indicator.
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DBUG((" max literals reached"));
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DBUG((" max literals reached\n"));
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*outPtr++ = 0xff; // literal-len=15, match-len=15
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*outPtr++ = MAX_LITERAL_LEN - INITIAL_LEN; // 240
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memcpy(outPtr, literalSrcPtr, numLiterals);
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@ -630,9 +634,12 @@ size_t compressBufferGreedily(uint8_t* outBuf, const uint8_t* inBuf,
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// Dump any remaining literals, with the end-of-data indicator
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// in the match len.
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if (numLiterals <= INITIAL_LEN) {
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DBUG(("ending with numLiterals=%zd\n", numLiterals));
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if (numLiterals < INITIAL_LEN) {
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// 0-14 literals, only need the nibble
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*outPtr++ = (numLiterals << 4) | 0x0f;
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} else {
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// 15-255 literals, need the extra byte
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*outPtr++ = 0xff;
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*outPtr++ = numLiterals - INITIAL_LEN;
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}
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@ -673,7 +680,9 @@ size_t uncompressBuffer(uint8_t* outBuf, const uint8_t* inBuf, size_t inLen)
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DBUG(("Literals: %d\n", literalLen));
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if ((outPtr - outBuf) + literalLen > (long) MAX_SIZE ||
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(inPtr - inBuf) + literalLen > (long) inLen) {
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fprintf(stderr, "Buffer overrun\n");
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fprintf(stderr,
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"Buffer overrun L: outPosn=%zd inPosn=%zd len=%d inLen=%ld\n",
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outPtr - outBuf, inPtr - inBuf, literalLen, inLen);
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return 0;
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}
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memcpy(outPtr, inPtr, literalLen);
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@ -707,7 +716,9 @@ size_t uncompressBuffer(uint8_t* outBuf, const uint8_t* inBuf, size_t inLen)
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uint8_t* srcPtr = outBuf + matchOffset;
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if ((outPtr - outBuf) + matchLen > MAX_SIZE ||
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(srcPtr - outBuf) + matchLen > MAX_SIZE) {
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fprintf(stderr, "Buffer overrun\n");
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fprintf(stderr,
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"Buffer overrun M: outPosn=%zd srcPosn=%zd len=%d\n",
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outPtr - outBuf, srcPtr - outBuf, matchLen);
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return 0;
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}
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while (matchLen-- != 0) {
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@ -14,6 +14,74 @@
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const char* TEST_ALL_ZERO = "allzero#060000";
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const char* TEST_ALL_GREEN = "allgreen#060000";
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const char* TEST_NO_MATCH = "nomatch#060000";
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const char* TEST_HALF_HALF = "halfhalf#060000";
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// Generates a pattern that foils the matcher.
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static void WriteNoMatch(FILE* fp)
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{
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for (int ic = 0; ic < 252; ic++) {
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putc(ic, fp);
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putc(ic+1, fp);
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putc(ic+2, fp);
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putc(ic+3, fp);
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}
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// 1008
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for (int ic = 0; ic < 252; ic++) {
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putc(ic, fp);
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putc(ic+2, fp);
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putc(ic+1, fp);
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putc(ic+3, fp);
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}
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// 2016
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for (int ic = 0; ic < 252; ic++) {
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putc(ic, fp);
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putc(ic+1, fp);
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putc(ic+3, fp);
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putc(ic+2, fp);
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}
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// 3024
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for (int ic = 0; ic < 252; ic++) {
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putc(ic, fp);
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putc(ic+3, fp);
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putc(ic+2, fp);
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putc(ic+1, fp);
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}
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// 4032
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for (int ic = 0; ic < 252; ic++) {
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putc(ic, fp);
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putc(ic+3, fp);
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putc(ic+1, fp);
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putc(ic+2, fp);
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}
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// 5040
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for (int ic = 0; ic < 252; ic++) {
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putc(ic+1, fp);
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putc(ic, fp);
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putc(ic+2, fp);
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putc(ic+3, fp);
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}
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// 6048
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for (int ic = 0; ic < 252; ic++) {
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putc(ic+1, fp);
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putc(ic+2, fp);
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putc(ic, fp);
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putc(ic+3, fp);
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}
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// 7056
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for (int ic = 0; ic < 252; ic++) {
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putc(ic+1, fp);
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putc(ic+2, fp);
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putc(ic+3, fp);
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putc(ic, fp);
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}
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// 8064
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for (int ic = 0; ic < 32; ic++) {
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putc(ic+2, fp);
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putc(ic+1, fp);
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putc(ic+3, fp);
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putc(ic, fp);
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}
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}
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int main()
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{
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@ -44,71 +112,22 @@ int main()
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printf("NOT overwriting %s\n", TEST_NO_MATCH);
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} else {
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fp = fopen(TEST_NO_MATCH, "w");
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for (int ic = 0; ic < 252; ic++) {
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putc(ic, fp);
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putc(ic+1, fp);
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putc(ic+2, fp);
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putc(ic+3, fp);
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}
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// 1008
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for (int ic = 0; ic < 252; ic++) {
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putc(ic, fp);
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putc(ic+2, fp);
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putc(ic+1, fp);
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putc(ic+3, fp);
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}
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// 2016
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for (int ic = 0; ic < 252; ic++) {
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putc(ic, fp);
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putc(ic+1, fp);
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putc(ic+3, fp);
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putc(ic+2, fp);
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}
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// 3024
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for (int ic = 0; ic < 252; ic++) {
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putc(ic, fp);
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putc(ic+3, fp);
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putc(ic+2, fp);
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putc(ic+1, fp);
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}
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// 4032
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for (int ic = 0; ic < 252; ic++) {
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putc(ic, fp);
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putc(ic+3, fp);
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putc(ic+1, fp);
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putc(ic+2, fp);
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}
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// 5040
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for (int ic = 0; ic < 252; ic++) {
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putc(ic+1, fp);
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putc(ic, fp);
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putc(ic+2, fp);
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putc(ic+3, fp);
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}
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// 6048
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for (int ic = 0; ic < 252; ic++) {
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putc(ic+1, fp);
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putc(ic+2, fp);
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putc(ic, fp);
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putc(ic+3, fp);
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}
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// 7056
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for (int ic = 0; ic < 252; ic++) {
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putc(ic+1, fp);
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putc(ic+2, fp);
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putc(ic+3, fp);
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putc(ic, fp);
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}
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// 8064
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for (int ic = 0; ic < 32; ic++) {
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putc(ic+2, fp);
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putc(ic+1, fp);
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putc(ic+3, fp);
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putc(ic, fp);
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}
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WriteNoMatch(fp);
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fclose(fp);
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}
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if (access(TEST_HALF_HALF, F_OK) == 0) {
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printf("NOT overwriting %s\n", TEST_HALF_HALF);
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} else {
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fp = fopen(TEST_HALF_HALF, "w");
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for (int i = 0; i < 4096; i++) {
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putc(0x00, fp);
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}
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WriteNoMatch(fp);
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fclose(fp);
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truncate(TEST_HALF_HALF, 8192);
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}
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return 0;
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}
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