Revision 663b2b1b90bf76275044824ddeca96aaec240f09 authored by Derrick Stolee on 17 September 2020, 18:11:46 UTC, committed by Junio C Hamano on 17 September 2020, 18:30:05 UTC
The first new task in the 'git maintenance' builtin is the 'commit-graph' task. This updates the commit-graph file incrementally with the command git commit-graph write --reachable --split By writing an incremental commit-graph file using the "--split" option we minimize the disruption from this operation. The default behavior is to merge layers until the new "top" layer is less than half the size of the layer below. This provides quick writes most of the time, with the longer writes following a power law distribution. Most importantly, concurrent Git processes only look at the commit-graph-chain file for a very short amount of time, so they will verly likely not be holding a handle to the file when we try to replace it. (This only matters on Windows.) If a concurrent process reads the old commit-graph-chain file, but our job expires some of the .graph files before they can be read, then those processes will see a warning message (but not fail). This could be avoided by a future update to use the --expire-time argument when writing the commit-graph. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent 3103e98
base85.c
#include "cache.h"
#undef DEBUG_85
#ifdef DEBUG_85
#define say(a) fprintf(stderr, a)
#define say1(a,b) fprintf(stderr, a, b)
#define say2(a,b,c) fprintf(stderr, a, b, c)
#else
#define say(a) do { /* nothing */ } while (0)
#define say1(a,b) do { /* nothing */ } while (0)
#define say2(a,b,c) do { /* nothing */ } while (0)
#endif
static const char en85[] = {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
'U', 'V', 'W', 'X', 'Y', 'Z',
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
'u', 'v', 'w', 'x', 'y', 'z',
'!', '#', '$', '%', '&', '(', ')', '*', '+', '-',
';', '<', '=', '>', '?', '@', '^', '_', '`', '{',
'|', '}', '~'
};
static char de85[256];
static void prep_base85(void)
{
int i;
if (de85['Z'])
return;
for (i = 0; i < ARRAY_SIZE(en85); i++) {
int ch = en85[i];
de85[ch] = i + 1;
}
}
int decode_85(char *dst, const char *buffer, int len)
{
prep_base85();
say2("decode 85 <%.*s>", len / 4 * 5, buffer);
while (len) {
unsigned acc = 0;
int de, cnt = 4;
unsigned char ch;
do {
ch = *buffer++;
de = de85[ch];
if (--de < 0)
return error("invalid base85 alphabet %c", ch);
acc = acc * 85 + de;
} while (--cnt);
ch = *buffer++;
de = de85[ch];
if (--de < 0)
return error("invalid base85 alphabet %c", ch);
/* Detect overflow. */
if (0xffffffff / 85 < acc ||
0xffffffff - de < (acc *= 85))
return error("invalid base85 sequence %.5s", buffer-5);
acc += de;
say1(" %08x", acc);
cnt = (len < 4) ? len : 4;
len -= cnt;
do {
acc = (acc << 8) | (acc >> 24);
*dst++ = acc;
} while (--cnt);
}
say("\n");
return 0;
}
void encode_85(char *buf, const unsigned char *data, int bytes)
{
say("encode 85");
while (bytes) {
unsigned acc = 0;
int cnt;
for (cnt = 24; cnt >= 0; cnt -= 8) {
unsigned ch = *data++;
acc |= ch << cnt;
if (--bytes == 0)
break;
}
say1(" %08x", acc);
for (cnt = 4; cnt >= 0; cnt--) {
int val = acc % 85;
acc /= 85;
buf[cnt] = en85[val];
}
buf += 5;
}
say("\n");
*buf = 0;
}
#ifdef DEBUG_85
int main(int ac, char **av)
{
char buf[1024];
if (!strcmp(av[1], "-e")) {
int len = strlen(av[2]);
encode_85(buf, av[2], len);
if (len <= 26) len = len + 'A' - 1;
else len = len + 'a' - 26 - 1;
printf("encoded: %c%s\n", len, buf);
return 0;
}
if (!strcmp(av[1], "-d")) {
int len = *av[2];
if ('A' <= len && len <= 'Z') len = len - 'A' + 1;
else len = len - 'a' + 26 + 1;
decode_85(buf, av[2]+1, len);
printf("decoded: %.*s\n", len, buf);
return 0;
}
if (!strcmp(av[1], "-t")) {
char t[4] = { -1,-1,-1,-1 };
encode_85(buf, t, 4);
printf("encoded: D%s\n", buf);
return 0;
}
}
#endif
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