git

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#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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