[PATCH 01/10] strbuf: Add strbuf_read_noblock

[Stefan Beller <sbeller@google.com>]

We need to read from pipes without blocking in a later patch.

Signed-off-by: Stefan Beller <sbeller@google.com>
---
 strbuf.c | 25 +++++++++++++++++++++++--
 strbuf.h |  6 ++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/strbuf.c b/strbuf.c
index cce5eed..4130ee2 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -357,7 +357,10 @@ size_t strbuf_fread(struct strbuf *sb, size_t size, FILE *f)
 	return res;
 }
 
-ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint)
+#define IGNORE_EAGAIN (1)
+
+static ssize_t strbuf_read_internal(struct strbuf *sb, int fd,
+				    size_t hint, int flags)
 {
 	size_t oldlen = sb->len;
 	size_t oldalloc = sb->alloc;
@@ -366,8 +369,16 @@ ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint)
 	for (;;) {
 		ssize_t cnt;
 
-		cnt = xread(fd, sb->buf + sb->len, sb->alloc - sb->len - 1);
+		cnt = read(fd, sb->buf + sb->len, sb->alloc - sb->len - 1);
 		if (cnt < 0) {
+			if (errno == EINTR)
+				continue;
+			if (errno == EAGAIN) {
+				if (flags & IGNORE_EAGAIN)
+					break;
+				else
+					continue;
+			}
 			if (oldalloc == 0)
 				strbuf_release(sb);
 			else
@@ -384,6 +395,16 @@ ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint)
 	return sb->len - oldlen;
 }
 
+ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint)
+{
+	return strbuf_read_internal(sb, fd, hint, 0);
+}
+
+ssize_t strbuf_read_noblock(struct strbuf *sb, int fd, size_t hint)
+{
+	return strbuf_read_internal(sb, fd, hint, IGNORE_EAGAIN);
+}
+
 #define STRBUF_MAXLINK (2*PATH_MAX)
 
 int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint)
diff --git a/strbuf.h b/strbuf.h
index aef2794..23ca7aa 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -367,6 +367,12 @@ extern size_t strbuf_fread(struct strbuf *, size_t, FILE *);
 extern ssize_t strbuf_read(struct strbuf *, int fd, size_t hint);
 
 /**
+ * Same as strbuf_read, just returns non-blockingly by ignoring EAGAIN.
+ * The fd must have set O_NONBLOCK.
+ */
+extern ssize_t strbuf_read_noblock(struct strbuf *, int fd, size_t hint);
+
+/**
  * Read the contents of a file, specified by its path. The third argument
  * can be used to give a hint about the file size, to avoid reallocs.
  */
-- 
2.6.0.rc0.131.gf624c3d