strbuf: add strbuf_read_once to read without blocking
The new call will read from a file descriptor into a strbuf once. The underlying call xread is just run once. xread only reattempts reading in case of EINTR, which makes it suitable to use for a nonblocking read. Signed-off-by: Stefan Beller <sbeller@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Stefan Beller committed
Dec 15, 2015 at 16:04 UTC
b4e04fb66e87a027c5f9c96bcbbba50719400169
2 files changed
+19
strbuf.c
+11
@@ -384,6 +384,17 @@ ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint)
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return sb->len - oldlen;
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}
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+ssize_t strbuf_read_once(struct strbuf *sb, int fd, size_t hint)
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+{
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+ ssize_t cnt;
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+
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+ strbuf_grow(sb, hint ? hint : 8192);
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+ cnt = xread(fd, sb->buf + sb->len, sb->alloc - sb->len - 1);
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+ if (cnt > 0)
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+ strbuf_setlen(sb, sb->len + cnt);
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+ return cnt;
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+}
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+
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#define STRBUF_MAXLINK (2*PATH_MAX)
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int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint)
strbuf.h
+8
@@ -366,6 +366,14 @@ extern size_t strbuf_fread(struct strbuf *, size_t, FILE *);
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*/
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extern ssize_t strbuf_read(struct strbuf *, int fd, size_t hint);
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+/**
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+ * Read the contents of a given file descriptor partially by using only one
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+ * attempt of xread. The third argument can be used to give a hint about the
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+ * file size, to avoid reallocs. Returns the number of new bytes appended to
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+ * the sb.
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+ */
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+extern ssize_t strbuf_read_once(struct strbuf *, int fd, size_t hint);
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+
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/**
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* Read the contents of a file, specified by its path. The third argument
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* can be used to give a hint about the file size, to avoid reallocs.