From b11b7e13f48ee283738e21fea9f775cd40ca0562 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 17 Dec 2008 09:36:40 -0800 Subject: [PATCH] Add generic 'strbuf_readlink()' helper function It was already what 'git apply' did in read_old_data(), just export it as a real function, and make it be more generic. In particular, this handles the case of the lstat() st_size data not matching the readlink() return value properly (which apparently happens at least on NTFS under Linux). But as a result of this you could also use the new function without even knowing how big the link is going to be, and it will allocate an appropriately sized buffer. So we pass in the st_size of the link as just a hint, rather than a fixed requirement. Signed-off-by: Linus Torvalds Signed-off-by: Junio C Hamano --- builtin-apply.c | 6 ++---- strbuf.c | 27 +++++++++++++++++++++++++++ strbuf.h | 1 + 3 files changed, 30 insertions(+), 4 deletions(-) diff --git a/builtin-apply.c b/builtin-apply.c index 4c4d1e1774..07244b0736 100644 --- a/builtin-apply.c +++ b/builtin-apply.c @@ -1559,10 +1559,8 @@ static int read_old_data(struct stat *st, const char *path, struct strbuf *buf) { switch (st->st_mode & S_IFMT) { case S_IFLNK: - strbuf_grow(buf, st->st_size); - if (readlink(path, buf->buf, st->st_size) != st->st_size) - return -1; - strbuf_setlen(buf, st->st_size); + if (strbuf_readlink(buf, path, st->st_size) < 0) + return error("unable to read symlink %s", path); return 0; case S_IFREG: if (strbuf_read_file(buf, path, st->st_size) != st->st_size) diff --git a/strbuf.c b/strbuf.c index 13be67e4d3..bdf49544d4 100644 --- a/strbuf.c +++ b/strbuf.c @@ -288,6 +288,33 @@ ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint) return sb->len - oldlen; } +#define STRBUF_MAXLINK (2*PATH_MAX) + +int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint) +{ + if (hint < 32) + hint = 32; + + while (hint < STRBUF_MAXLINK) { + int len; + + strbuf_grow(sb, hint); + len = readlink(path, sb->buf, hint); + if (len < 0) { + if (errno != ERANGE) + break; + } else if (len < hint) { + strbuf_setlen(sb, len); + return 0; + } + + /* .. the buffer was too small - try again */ + hint *= 2; + } + strbuf_release(sb); + return -1; +} + int strbuf_getline(struct strbuf *sb, FILE *fp, int term) { int ch; diff --git a/strbuf.h b/strbuf.h index b1670d9945..89bd36e15a 100644 --- a/strbuf.h +++ b/strbuf.h @@ -124,6 +124,7 @@ extern size_t strbuf_fread(struct strbuf *, size_t, FILE *); /* XXX: if read fails, any partial read is undone */ extern ssize_t strbuf_read(struct strbuf *, int fd, size_t hint); extern int strbuf_read_file(struct strbuf *sb, const char *path, size_t hint); +extern int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint); extern int strbuf_getline(struct strbuf *, FILE *, int); -- 2.11.4.GIT