[hackers] [flate] +crc +adler +flatez (zlib+gz) || nsz

changeset: 109:5db820477dec
user: nsz <nszabolcs_AT_gmail.com>
date: Tue Aug 18 23:49:20 2009 +0200
files: adler.c crc.c flatez.c
description:
+crc +adler +flatez (zlib+gz)

diff -r e519cc4f1716 -r 5db820477dec adler.c
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/adler.c Tue Aug 18 23:49:20 2009 +0200
@@ -0,0 +1,61 @@
+enum {
+ AdlerBase = 65521, /* largest 16bit prime */
+ AdlerN = 5552 /* max iters before 32bit overflow */
+};
+
+uint adlersum(uchar *p, int n, uint adler) {
+ uint s1 = adler & 0xffff;
+ uint s2 = (adler >> 16) & 0xffff;
+ uchar *ep;
+ int k;
+
+ for (; n >= 16; n -= k) {
+ k = n < AdlerN ? n : AdlerN;
+ k &= ~0xf;
+ for (ep = p + k; p < ep; p += 16) {
+ s1 += p[0];
+ s2 += s1;
+ s1 += p[1];
+ s2 += s1;
+ s1 += p[2];
+ s2 += s1;
+ s1 += p[3];
+ s2 += s1;
+ s1 += p[4];
+ s2 += s1;
+ s1 += p[5];
+ s2 += s1;
+ s1 += p[6];
+ s2 += s1;
+ s1 += p[7];
+ s2 += s1;
+ s1 += p[8];
+ s2 += s1;
+ s1 += p[9];
+ s2 += s1;
+ s1 += p[10];
+ s2 += s1;
+ s1 += p[11];
+ s2 += s1;
+ s1 += p[12];
+ s2 += s1;
+ s1 += p[13];
+ s2 += s1;
+ s1 += p[14];
+ s2 += s1;
+ s1 += p[15];
+ s2 += s1;
+ }
+ s1 %= AdlerBase;
+ s2 %= AdlerBase;
+ }
+ if (n) {
+ for (ep = p + n; p < ep; p++) {
+ s1 += p[0];
+ s2 += s1;
+ }
+ s1 %= AdlerBase;
+ s2 %= AdlerBase;
+ }
+ return (s2 << 16) + s1;
+}
diff -r e519cc4f1716 -r 5db820477dec crc.c
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/crc.c Tue Aug 18 23:49:20 2009 +0200
@@ -0,0 +1,25 @@
+uint crctab[256];
+
+void crcinit(void) {
+ static const uint poly = 0xEDB88320;
+
+ for (i = 0; i < 256; ++i) {
+ crc = i;
+ for (j = 0; j < 8; j++) {
+ if (crc & 1)
+ crc = (crc >> 1) ^ poly;
+ else
+ crc >>= 1;
+ }
+ crctab[i] = crc;
+ }
+}
+
+uint crcsum(uchar *p, int n, uint crc) {
+ uchar *ep = p + n;
+
+ crc ^= 0xffffffff;
+ while (p < ep)
+ crc = crctab[(crc & 0xff) ^ *buf++] ^ (crc >> 8);
+ return crc ^ 0xffffffff;
+}
diff -r e519cc4f1716 -r 5db820477dec flatez.c
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/flatez.c Tue Aug 18 23:49:20 2009 +0200
@@ -0,0 +1,132 @@
+
+static int checkfooter(uchar *p, uint sum) {
+ return sum == ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3]);
+}
+
+enum {
+ ZlibCM = 7 << 4,
+ ZlibCINFO = 8,
+ ZlibFLEV = 3 << 6,
+ ZlibFDICT = 1 << 5,
+ ZlibFCHK = 31 - (((ZlibCM | ZlibCINFO) << 8) | ZlibFLEV) % 31,
+};
+
+int deflate_zlib_header(uchar *p, int n) {
+ if (n < 2)
+ return FlateErr;
+ p[0] = ZlibCM | ZlibCINFO; /* deflate method, 32K window size */
+ p[1] = ZlibFLEV | ZlibFCHK; /* highest compression */
+ return 2;
+}
+
+int deflate_zlib_footer(uchar *p, int n, uint sum) {
+ if (n < 4)
+ return FlateErr;
+ p[0] = sum >> 24;
+ p[1] = sum >> 16;
+ p[2] = sum >> 8;
+ p[3] = sum;
+ return 4;
+}
+
+int inflate_zlib_header(uchar *p, int n) {
+ if (n < 2)
+ return FlateErr;
+ if (((p[0] << 8) | p[1]) % 31)
+ return FlateErr;
+ if ((p[0] & 0xf0) != ZlibCM || (p[0] & 0x0f) > ZlibCINFO)
+ return FlateErr;
+ if (p[1] & ZlibFDICT)
+ return FlateErr;
+ return 2;
+}
+
+int inflate_zlib_footer(uchar *p, int n, uint sum) {
+ if (n < 4 || !checkfooter(p, sum))
+ return FlateErr;
+ return 4;
+}
+
+
+enum {
+ GZipID1 = 0x1f,
+ GZipID2 = 0x8b,
+ GZipCM = 8,
+ GZipFHCRC = 1 << 1,
+ GZipFEXTRA = 1 << 2,
+ GZipFNAME = 1 << 3,
+ GZipFCOMM = 1 << 4,
+ GZipXFL = 2,
+ GZipOS = 255
+};
+
+int deflate_gzip_header(uchar *p, int n) {
+ int k;
+
+ if (n < 10)
+ return FlateErr;
+ for (k = 0; k < n; k++)
+ p[k] = 0;
+ p[0] = GZipID1;
+ p[1] = GZipID2;
+ p[2] = GZipCM;
+ p[8] = GZipXFL;
+ p[9] = GZipOS;
+ return 10;
+}
+
+int deflate_gzip_footer(uchar *p, int n, uint sum, uint len) {
+ if (n < 8)
+ return FlateErr;
+ p[0] = sum >> 24;
+ p[1] = sum >> 16;
+ p[2] = sum >> 8;
+ p[3] = sum;
+ p[4] = len >> 24;
+ p[5] = len >> 16;
+ p[6] = len >> 8;
+ p[7] = len;
+ return 8;
+}
+
+int inflate_gzip_header(uchar *p, int n) {
+ int k = 10;
+
+ if (k > n)
+ return FlateErr;
+ if (p[0] != GZipID1 || p[1] != GZipID2 || p[2] != GZipCM)
+ return FlateErr;
+ if (p[3] & GZipFEXTRA) {
+ k += 2 + ((p[k] << 8) | p[k+1]);
+ if (k > n)
+ return FlateErr;
+ }
+ if (p[3] & GZipFNAME) {
+ for (; k < n; k++)
+ if (p[k] == 0)
+ break;
+ k++;
+ if (k > n)
+ return FlateErr;
+ }
+ if (p[3] & GZipFCOMM) {
+ for (; k < n; k++)
+ if (p[k] == 0)
+ break;
+ k++;
+ if (k > n)
+ return FlateErr;
+ }
+ if (p[3] & GZipFHCRC) {
+ k += 2;
+ if (k > n)
+ return FlateErr;
+ }
+ return k;
+}
+
+int inflate_gzip_footer(uchar *p, int n, uint sum, uint len) {
+ if (n < 8 || !checkfooter(p, sum) || !checkfooter(p+4, len))
+ return FlateErr;
+ return 8;
+}
Received on Fri Aug 21 2009 - 13:50:15 UTC