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cde75e59e1
Some of the --pretty=format placeholders expansions are expensive to
calculate. This is made worse by the current code's use of
interpolate(), which requires _all_ placeholders are to be prepared
up front.
One way to speed this up is to check which placeholders are present
in the format string and to prepare only the expansions that are
needed. That still leaves the allocation overhead of interpolate().
Another way is to use a callback based approach together with the
strbuf library to keep allocations to a minimum and avoid string
copies. That's what this patch does. It introduces a new strbuf
function, strbuf_expand().
The function takes a format string, list of placeholder strings,
a user supplied function 'fn', and an opaque pointer 'context'
to tell 'fn' what thingy to operate on.
The function 'fn' is expected to accept a strbuf, a parsed
placeholder string and the 'context' pointer, and append the
interpolated value for the 'context' thingy, according to the
format specified by the placeholder.
Thanks to Pierre Habouzit for his suggestion to use strchrnul() and
the code surrounding its callsite. And thanks to Junio for most of
this commit message. :)
Here my measurements of most of Paul Mackerras' test cases that
highlighted the performance problem (best of three runs):
(master)
$ time git log --pretty=oneline >/dev/null
real 0m0.390s
user 0m0.340s
sys 0m0.040s
(master)
$ time git log --pretty=raw >/dev/null
real 0m0.434s
user 0m0.408s
sys 0m0.016s
(master)
$ time git log --pretty="format:%H {%P} %ct" >/dev/null
real 0m1.347s
user 0m0.080s
sys 0m1.256s
(interp_find_active -- Dscho)
$ time ./git log --pretty="format:%H {%P} %ct" >/dev/null
real 0m0.694s
user 0m0.020s
sys 0m0.672s
(strbuf_expand -- this patch)
$ time ./git log --pretty="format:%H {%P} %ct" >/dev/null
real 0m0.395s
user 0m0.352s
sys 0m0.028s
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
121 lines
4.1 KiB
C
121 lines
4.1 KiB
C
#ifndef STRBUF_H
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#define STRBUF_H
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/*
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* Strbuf's can be use in many ways: as a byte array, or to store arbitrary
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* long, overflow safe strings.
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*
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* Strbufs has some invariants that are very important to keep in mind:
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*
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* 1. the ->buf member is always malloc-ed, hence strbuf's can be used to
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* build complex strings/buffers whose final size isn't easily known.
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*
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* It is NOT legal to copy the ->buf pointer away.
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* `strbuf_detach' is the operation that detachs a buffer from its shell
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* while keeping the shell valid wrt its invariants.
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*
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* 2. the ->buf member is a byte array that has at least ->len + 1 bytes
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* allocated. The extra byte is used to store a '\0', allowing the ->buf
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* member to be a valid C-string. Every strbuf function ensure this
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* invariant is preserved.
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*
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* Note that it is OK to "play" with the buffer directly if you work it
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* that way:
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*
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* strbuf_grow(sb, SOME_SIZE);
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* ... Here, the memory array starting at sb->buf, and of length
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* ... strbuf_avail(sb) is all yours, and you are sure that
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* ... strbuf_avail(sb) is at least SOME_SIZE.
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* strbuf_setlen(sb, sb->len + SOME_OTHER_SIZE);
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*
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* Of course, SOME_OTHER_SIZE must be smaller or equal to strbuf_avail(sb).
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*
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* Doing so is safe, though if it has to be done in many places, adding the
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* missing API to the strbuf module is the way to go.
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*
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* XXX: do _not_ assume that the area that is yours is of size ->alloc - 1
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* even if it's true in the current implementation. Alloc is somehow a
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* "private" member that should not be messed with.
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*/
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#include <assert.h>
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extern char strbuf_slopbuf[];
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struct strbuf {
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size_t alloc;
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size_t len;
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char *buf;
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};
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#define STRBUF_INIT { 0, 0, strbuf_slopbuf }
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/*----- strbuf life cycle -----*/
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extern void strbuf_init(struct strbuf *, size_t);
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extern void strbuf_release(struct strbuf *);
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extern char *strbuf_detach(struct strbuf *, size_t *);
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extern void strbuf_attach(struct strbuf *, void *, size_t, size_t);
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static inline void strbuf_swap(struct strbuf *a, struct strbuf *b) {
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struct strbuf tmp = *a;
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*a = *b;
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*b = tmp;
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}
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/*----- strbuf size related -----*/
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static inline size_t strbuf_avail(struct strbuf *sb) {
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return sb->alloc ? sb->alloc - sb->len - 1 : 0;
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}
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extern void strbuf_grow(struct strbuf *, size_t);
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static inline void strbuf_setlen(struct strbuf *sb, size_t len) {
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if (!sb->alloc)
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strbuf_grow(sb, 0);
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assert(len < sb->alloc);
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sb->len = len;
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sb->buf[len] = '\0';
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}
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#define strbuf_reset(sb) strbuf_setlen(sb, 0)
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/*----- content related -----*/
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extern void strbuf_rtrim(struct strbuf *);
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extern int strbuf_cmp(struct strbuf *, struct strbuf *);
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/*----- add data in your buffer -----*/
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static inline void strbuf_addch(struct strbuf *sb, int c) {
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strbuf_grow(sb, 1);
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sb->buf[sb->len++] = c;
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sb->buf[sb->len] = '\0';
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}
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extern void strbuf_insert(struct strbuf *, size_t pos, const void *, size_t);
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extern void strbuf_remove(struct strbuf *, size_t pos, size_t len);
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/* splice pos..pos+len with given data */
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extern void strbuf_splice(struct strbuf *, size_t pos, size_t len,
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const void *, size_t);
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extern void strbuf_add(struct strbuf *, const void *, size_t);
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static inline void strbuf_addstr(struct strbuf *sb, const char *s) {
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strbuf_add(sb, s, strlen(s));
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}
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static inline void strbuf_addbuf(struct strbuf *sb, struct strbuf *sb2) {
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strbuf_add(sb, sb2->buf, sb2->len);
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}
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typedef void (*expand_fn_t) (struct strbuf *sb, const char *placeholder, void *context);
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extern void strbuf_expand(struct strbuf *sb, const char *format, const char **placeholders, expand_fn_t fn, void *context);
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__attribute__((format(printf,2,3)))
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extern void strbuf_addf(struct strbuf *sb, const char *fmt, ...);
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extern size_t strbuf_fread(struct strbuf *, size_t, FILE *);
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/* XXX: if read fails, any partial read is undone */
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extern ssize_t strbuf_read(struct strbuf *, int fd, size_t hint);
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extern int strbuf_read_file(struct strbuf *sb, const char *path, size_t hint);
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extern int strbuf_getline(struct strbuf *, FILE *, int);
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extern void stripspace(struct strbuf *buf, int skip_comments);
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#endif /* STRBUF_H */
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