134 lines
2.8 KiB
C
134 lines
2.8 KiB
C
#include "git-compat-util.h"
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#include "base85.h"
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#undef DEBUG_85
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#ifdef DEBUG_85
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#define say(a) fprintf(stderr, a)
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#define say1(a,b) fprintf(stderr, a, b)
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#define say2(a,b,c) fprintf(stderr, a, b, c)
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#else
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#define say(a) do { /* nothing */ } while (0)
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#define say1(a,b) do { /* nothing */ } while (0)
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#define say2(a,b,c) do { /* nothing */ } while (0)
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#endif
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static const char en85[] = {
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'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
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'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
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'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
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'U', 'V', 'W', 'X', 'Y', 'Z',
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'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
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'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
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'u', 'v', 'w', 'x', 'y', 'z',
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'!', '#', '$', '%', '&', '(', ')', '*', '+', '-',
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';', '<', '=', '>', '?', '@', '^', '_', '`', '{',
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'|', '}', '~'
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};
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static char de85[256];
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static void prep_base85(void)
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{
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int i;
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if (de85['Z'])
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return;
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for (i = 0; i < ARRAY_SIZE(en85); i++) {
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int ch = en85[i];
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de85[ch] = i + 1;
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}
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}
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int decode_85(char *dst, const char *buffer, int len)
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{
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prep_base85();
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say2("decode 85 <%.*s>", len / 4 * 5, buffer);
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while (len) {
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unsigned acc = 0;
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int de, cnt = 4;
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unsigned char ch;
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do {
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ch = *buffer++;
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de = de85[ch];
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if (--de < 0)
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return error("invalid base85 alphabet %c", ch);
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acc = acc * 85 + de;
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} while (--cnt);
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ch = *buffer++;
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de = de85[ch];
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if (--de < 0)
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return error("invalid base85 alphabet %c", ch);
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/* Detect overflow. */
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if (0xffffffff / 85 < acc ||
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0xffffffff - de < (acc *= 85))
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return error("invalid base85 sequence %.5s", buffer-5);
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acc += de;
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say1(" %08x", acc);
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cnt = (len < 4) ? len : 4;
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len -= cnt;
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do {
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acc = (acc << 8) | (acc >> 24);
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*dst++ = acc;
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} while (--cnt);
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}
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say("\n");
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return 0;
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}
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void encode_85(char *buf, const unsigned char *data, int bytes)
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{
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say("encode 85");
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while (bytes) {
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unsigned acc = 0;
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int cnt;
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for (cnt = 24; cnt >= 0; cnt -= 8) {
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unsigned ch = *data++;
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acc |= ch << cnt;
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if (--bytes == 0)
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break;
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}
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say1(" %08x", acc);
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for (cnt = 4; cnt >= 0; cnt--) {
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int val = acc % 85;
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acc /= 85;
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buf[cnt] = en85[val];
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}
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buf += 5;
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}
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say("\n");
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*buf = 0;
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}
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#ifdef DEBUG_85
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int main(int ac, char **av)
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{
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char buf[1024];
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if (!strcmp(av[1], "-e")) {
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int len = strlen(av[2]);
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encode_85(buf, av[2], len);
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if (len <= 26) len = len + 'A' - 1;
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else len = len + 'a' - 26 - 1;
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printf("encoded: %c%s\n", len, buf);
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return 0;
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}
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if (!strcmp(av[1], "-d")) {
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int len = *av[2];
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if ('A' <= len && len <= 'Z') len = len - 'A' + 1;
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else len = len - 'a' + 26 + 1;
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decode_85(buf, av[2]+1, len);
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printf("decoded: %.*s\n", len, buf);
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return 0;
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}
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if (!strcmp(av[1], "-t")) {
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char t[4] = { -1,-1,-1,-1 };
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encode_85(buf, t, 4);
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printf("encoded: D%s\n", buf);
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return 0;
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}
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}
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#endif
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