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Use local variables in hash calc to avoid aliasing

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This commit is contained in:
Russell Belfer 2013-07-24 13:11:11 -07:00
parent 18e9efc425
commit 427cc255df
1 changed files with 19 additions and 11 deletions
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30
src/hashsig.c
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@ -43,8 +43,8 @@ struct git_hashsig {
int considered; int considered;
}; };
#define HEAP_LCHILD_OF(I) (((I)*2)+1) #define HEAP_LCHILD_OF(I) (((I)<<1)+1)
#define HEAP_RCHILD_OF(I) (((I)*2)+2) #define HEAP_RCHILD_OF(I) (((I)<<1)+2)
#define HEAP_PARENT_OF(I) (((I)-1)>>1) #define HEAP_PARENT_OF(I) (((I)-1)>>1)
static void hashsig_heap_init(hashsig_heap *h, hashsig_cmp cmp) static void hashsig_heap_init(hashsig_heap *h, hashsig_cmp cmp)
@ -152,8 +152,9 @@ static void hashsig_initial_window(
hashsig_in_progress *prog) hashsig_in_progress *prog)
{ {
hashsig_state state, shift_n; hashsig_state state, shift_n;
int win_len; int win_len, saw_lf = prog->saw_lf;
const char *scan, *end; const char *scan, *end;
char *window = &prog->window[0];
/* init until we have processed at least HASHSIG_HASH_WINDOW data */ /* init until we have processed at least HASHSIG_HASH_WINDOW data */
@ -170,7 +171,7 @@ static void hashsig_initial_window(
while (scan < end && win_len < HASHSIG_HASH_WINDOW) { while (scan < end && win_len < HASHSIG_HASH_WINDOW) {
char ch = *scan++; char ch = *scan++;
if (!hashsig_include_char(ch, sig->opt, &prog->saw_lf)) if (!hashsig_include_char(ch, sig->opt, &saw_lf))
continue; continue;
state = (state * HASHSIG_HASH_SHIFT + ch) & HASHSIG_HASH_MASK; state = (state * HASHSIG_HASH_SHIFT + ch) & HASHSIG_HASH_MASK;
@ -180,7 +181,7 @@ static void hashsig_initial_window(
else else
shift_n = (shift_n * HASHSIG_HASH_SHIFT) & HASHSIG_HASH_MASK; shift_n = (shift_n * HASHSIG_HASH_SHIFT) & HASHSIG_HASH_MASK;
prog->window[win_len++] = ch; window[win_len++] = ch;
} }
/* insert initial hash if we just finished */ /* insert initial hash if we just finished */
@ -194,6 +195,7 @@ static void hashsig_initial_window(
prog->state = state; prog->state = state;
prog->win_len = win_len; prog->win_len = win_len;
prog->shift_n = shift_n; prog->shift_n = shift_n;
prog->saw_lf = saw_lf;
*data = scan; *data = scan;
} }
@ -206,22 +208,26 @@ static int hashsig_add_hashes(
{ {
const char *scan = data, *end = data + size; const char *scan = data, *end = data + size;
hashsig_state state, shift_n, rmv; hashsig_state state, shift_n, rmv;
int win_pos, saw_lf;
char *window = &prog->window[0];
if (prog->win_len < HASHSIG_HASH_WINDOW) if (prog->win_len < HASHSIG_HASH_WINDOW)
hashsig_initial_window(sig, &scan, size, prog); hashsig_initial_window(sig, &scan, size, prog);
state = prog->state; state = prog->state;
shift_n = prog->shift_n; shift_n = prog->shift_n;
saw_lf = prog->saw_lf;
win_pos = prog->win_pos;
/* advance window, adding new chars and removing old */ /* advance window, adding new chars and removing old */
for (; scan < end; ++scan) { for (; scan < end; ++scan) {
char ch = *scan; char ch = *scan;
if (!hashsig_include_char(ch, sig->opt, &prog->saw_lf)) if (!hashsig_include_char(ch, sig->opt, &saw_lf))
continue; continue;
rmv = shift_n * prog->window[prog->win_pos]; rmv = shift_n * window[win_pos];
state = (state - rmv) & HASHSIG_HASH_MASK; state = (state - rmv) & HASHSIG_HASH_MASK;
state = (state * HASHSIG_HASH_SHIFT) & HASHSIG_HASH_MASK; state = (state * HASHSIG_HASH_SHIFT) & HASHSIG_HASH_MASK;
@ -231,11 +237,13 @@ static int hashsig_add_hashes(
hashsig_heap_insert(&sig->maxs, (hashsig_t)state); hashsig_heap_insert(&sig->maxs, (hashsig_t)state);
sig->considered++; sig->considered++;
prog->window[prog->win_pos] = ch; window[win_pos] = ch;
prog->win_pos = (prog->win_pos + 1) % HASHSIG_HASH_WINDOW; win_pos = (win_pos + 1) % HASHSIG_HASH_WINDOW;
} }
prog->state = state; prog->state = state;
prog->saw_lf = saw_lf;
prog->win_pos = win_pos;
return 0; return 0;
} }
@ -296,7 +304,7 @@ int git_hashsig_create_fromfile(
const char *path, const char *path,
git_hashsig_option_t opts) git_hashsig_option_t opts)
{ {
char buf[4096]; char buf[0x1000];
ssize_t buflen = 0; ssize_t buflen = 0;
int error = 0, fd; int error = 0, fd;
hashsig_in_progress prog = HASHSIG_IN_PROGRESS_INIT; hashsig_in_progress prog = HASHSIG_IN_PROGRESS_INIT;