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Switch over tree descriptors to contain a pre-parsed entry 

This makes the tree descriptor contain a "struct name_entry" as part of
it, and it gets filled in so that it always contains a valid entry. On
some benchmarks, it improves performance by up to 15%.

That makes tree entry "extract" trivial, and means that we only actually
need to decode each tree entry just once: we decode the first one when
we initialize the tree descriptor, and each subsequent one when doing
"update_tree_entry()".  In particular, this means that we don't need to
do strlen() both at extract time _and_ at update time.

Finally, it also allows more sharing of code (entry_extract(), that
wanted a "struct name_entry", just got totally trivial, along with the
"tree_entry()" function).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Linus Torvalds 2007-03-21 10:09:56 -07:00 committed by Junio C Hamano
parent 6fda5e5180
commit 4651ece854
2 changed files with 57 additions and 62 deletions
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101
tree-walk.c
View File

@ -2,10 +2,42 @@
#include "tree-walk.h"
#include "tree.h"
static const char *get_mode(const char *str, unsigned int *modep)
{
unsigned char c;
unsigned int mode = 0;
while ((c = *str++) != ' ') {
if (c < '0' || c > '7')
return NULL;
mode = (mode << 3) + (c - '0');
}
*modep = mode;
return str;
}
static void decode_tree_entry(struct tree_desc *desc, const void *buf, unsigned long size)
{
const char *path;
unsigned int mode, len;
path = get_mode(buf, &mode);
if (!path)
die("corrupt tree file");
len = strlen(path) + 1;
/* Initialize the descriptor entry */
desc->entry.path = path;
desc->entry.mode = mode;
desc->entry.sha1 = (const unsigned char *)(path + len);
}
void init_tree_desc(struct tree_desc *desc, const void *buffer, unsigned long size)
{
desc->buffer = buffer;
desc->size = size;
if (size)
decode_tree_entry(desc, buffer, size);
}
void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1)
@ -36,78 +68,33 @@ static void entry_clear(struct name_entry *a)
static void entry_extract(struct tree_desc *t, struct name_entry *a)
{
a->sha1 = tree_entry_extract(t, &a->path, &a->mode);
*a = t->entry;
}
void update_tree_entry(struct tree_desc *desc)
{
const void *buf = desc->buffer;
const unsigned char *end = desc->entry.sha1 + 20;
unsigned long size = desc->size;
int len = strlen(buf) + 1 + 20;
unsigned long len = end - (const unsigned char *)buf;
if (size < len)
die("corrupt tree file");
desc->buffer = (char *) buf + len;
desc->size = size - len;
}
static const char *get_mode(const char *str, unsigned int *modep)
{
unsigned char c;
unsigned int mode = 0;
while ((c = *str++) != ' ') {
if (c < '0' || c > '7')
return NULL;
mode = (mode << 3) + (c - '0');
}
*modep = mode;
return str;
}
const unsigned char *tree_entry_extract(struct tree_desc *desc, const char **pathp, unsigned int *modep)
{
const void *tree = desc->buffer;
unsigned long size = desc->size;
int len = strlen(tree)+1;
const unsigned char *sha1 = (unsigned char *) tree + len;
const char *path;
unsigned int mode;
path = get_mode(tree, &mode);
if (!path || size < len + 20)
die("corrupt tree file");
*pathp = path;
*modep = canon_mode(mode);
return sha1;
buf = end;
size -= len;
desc->buffer = buf;
desc->size = size;
if (size)
decode_tree_entry(desc, buf, size);
}
int tree_entry(struct tree_desc *desc, struct name_entry *entry)
{
const void *tree = desc->buffer;
const char *path;
unsigned long len, size = desc->size;
if (!size)
if (!desc->size)
return 0;
path = get_mode(tree, &entry->mode);
if (!path)
die("corrupt tree file");
entry->path = path;
len = strlen(path);
path += len + 1;
entry->sha1 = (const unsigned char *) path;
path += 20;
len = path - (char *) tree;
if (len > size)
die("corrupt tree file");
desc->buffer = path;
desc->size = size - len;
*entry = desc->entry;
update_tree_entry(desc);
return 1;
}

18
tree-walk.h
View File

@ -1,17 +1,25 @@
#ifndef TREE_WALK_H
#define TREE_WALK_H
struct tree_desc {
const void *buffer;
unsigned int size;
};
struct name_entry {
const unsigned char *sha1;
const char *path;
unsigned int mode;
};
struct tree_desc {
const void *buffer;
struct name_entry entry;
unsigned int size;
};
static inline const unsigned char *tree_entry_extract(struct tree_desc *desc, const char **pathp, unsigned int *modep)
{
*pathp = desc->entry.path;
*modep = canon_mode(desc->entry.mode);
return desc->entry.sha1;
}
static inline int tree_entry_len(const char *name, const unsigned char *sha1)
{
return (char *)sha1 - (char *)name - 1;