The fd_buffer library is perhaps poorly named, because it does not
manage its own buffer. These functions provide the relevant
functionality from line_buffer for low-level, unbuffered (file
descriptor) I/O.
The purpose is to preserve convenience while avoiding deadlock that
could occur from too greedily reading ahead in the cat-blob-fd pipe.
(An alternative approach to achieve the same effect would be to
set the O_NONBLOCK flag on the pipe fd.)
Signed-off-by: Jonathan Nieder <jrnieder@xxxxxxxxx>
---
Makefile | 5 ++-
vcs-svn/fast_export.c | 45 ++++++++++------------------------
vcs-svn/fd_buffer.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++
vcs-svn/fd_buffer.h | 19 ++++++++++++++
4 files changed, 100 insertions(+), 34 deletions(-)
create mode 100644 vcs-svn/fd_buffer.c
create mode 100644 vcs-svn/fd_buffer.h
diff --git a/Makefile b/Makefile
index aa10288..844e3b4 100644
--- a/Makefile
+++ b/Makefile
@@ -1760,7 +1760,7 @@ ifndef NO_CURL
endif
XDIFF_OBJS = xdiff/xdiffi.o xdiff/xprepare.o xdiff/xutils.o xdiff/xemit.o \
xdiff/xmerge.o xdiff/xpatience.o
-VCSSVN_OBJS = vcs-svn/string_pool.o vcs-svn/line_buffer.o \
+VCSSVN_OBJS = vcs-svn/string_pool.o vcs-svn/line_buffer.o vcs-svn/fd_buffer.o \
vcs-svn/repo_tree.o vcs-svn/fast_export.o vcs-svn/svndump.o \
vcs-svn/sliding_window.o vcs-svn/svndiff.o
OBJECTS := $(GIT_OBJS) $(XDIFF_OBJS) $(VCSSVN_OBJS)
@@ -1889,7 +1889,8 @@ xdiff-interface.o $(XDIFF_OBJS): \
$(VCSSVN_OBJS): \
vcs-svn/obj_pool.h vcs-svn/trp.h vcs-svn/string_pool.h \
vcs-svn/line_buffer.h vcs-svn/repo_tree.h vcs-svn/fast_export.h \
- vcs-svn/sliding_window.h vcs-svn/svndump.h vcs-svn/svndiff.h
+ vcs-svn/sliding_window.h vcs-svn/svndump.h vcs-svn/svndiff.h \
+ vcs-svn/fd_buffer.h
endif
exec_cmd.s exec_cmd.o: EXTRA_CPPFLAGS = \
diff --git a/vcs-svn/fast_export.c b/vcs-svn/fast_export.c
index 0de498b..ebaab72 100644
--- a/vcs-svn/fast_export.c
+++ b/vcs-svn/fast_export.c
@@ -6,6 +6,7 @@
#include "git-compat-util.h"
#include "fast_export.h"
#include "line_buffer.h"
+#include "fd_buffer.h"
#include "repo_tree.h"
#include "string_pool.h"
#include "strbuf.h"
@@ -73,7 +74,7 @@ static int ends_with(const char *s, size_t len, const char *suffix)
return !memcmp(s + len - suffixlen, suffix, suffixlen);
}
-static int parse_cat_response_line(const char *header, size_t *len)
+static int parse_cat_response_line(const char *header, off_t *len)
{
size_t headerlen = strlen(header);
const char *type;
@@ -95,45 +96,25 @@ static int parse_cat_response_line(const char *header, size_t *len)
static struct strbuf response_line = STRBUF_INIT;
static const char *get_response_line(void)
{
- /*
- * NEEDSWORK: Does not actually need to read one byte at a time.
- * Some platforms have O_NONBLOCK. On others we could read 8 chars
- * at a time until a potential appearance of " blob ".
- */
strbuf_reset(&response_line);
- for (;;) {
- char buf[1];
- if (xread(REPORT_FILENO, buf, 1) < 0) {
- error("cannot read cat-blob result: %s", strerror(errno));
- return NULL;
- }
- if (*buf == '\n')
- return response_line.buf;
- strbuf_addch(&response_line, *buf);
- }
+ if (fd_read_line(&response_line, REPORT_FILENO))
+ return NULL;
+ return response_line.buf;
}
-static int copy_bytes(FILE *out, size_t len)
+static int copy_bytes(FILE *out, off_t len)
{
- char buf[4096];
- ssize_t nread;
- for (; len; len -= nread) {
- nread = xread(REPORT_FILENO, buf,
- len < sizeof(buf) ? len : sizeof(buf));
- if (nread < 0)
- return error("cannot copy cat-blob result: %s",
- strerror(errno));
- if (!nread)
- return error("0-length read...");
- if (fwrite(buf, 1, nread, out) != nread)
- return error("cannot write cat-blob results: %s",
- strerror(errno));
- }
+ off_t ret = fd_copy_bytes(out, REPORT_FILENO, len);
+ if (!ret)
+ return error("read error: file ends early");
+ if (ret <= 0)
+ return error("cannot copy cat-blob result");
+ return 0;
}
static int fast_export_save_blob(FILE *out)
{
- size_t len = len;
+ off_t len = len;
const char *header, *tail;
header = get_response_line();
diff --git a/vcs-svn/fd_buffer.c b/vcs-svn/fd_buffer.c
new file mode 100644
index 0000000..3d2c1a1
--- /dev/null
+++ b/vcs-svn/fd_buffer.c
@@ -0,0 +1,65 @@
+/*
+ * Licensed under a two-clause BSD-style license.
+ * See LICENSE for details.
+ */
+
+#include "git-compat-util.h"
+#include "fd_buffer.h"
+#include "strbuf.h"
+
+/* Read a line without trailing newline. */
+int fd_read_line(struct strbuf *line, int fd)
+{
+ /*
+ * NEEDSWORK: Does not actually need to read one byte at a time.
+ * Some platforms have O_NONBLOCK. On others we could read
+ * several chars at a time until an appearance of a string known
+ * to belong in the line (e.g., " blob ").
+ */
+ for (;;) {
+ char buf[1];
+ if (xread(fd, buf, 1) < 0)
+ return error("cannot read line: %s", strerror(errno));
+ if (*buf == '\n')
+ return 0;
+ strbuf_addch(line, *buf);
+ }
+}
+
+int fd_read_binary(struct strbuf *buf, size_t len, int fd)
+{
+ char *p, *end;
+ strbuf_grow(buf, len);
+ p = buf->buf + buf->len;
+ end = p + len;
+
+ while (p != end) {
+ ssize_t nread = xread(fd, p, end - p);
+ if (nread < 0)
+ return error("read error: %s", strerror(errno));
+ if (!nread) /* end of file */
+ break;
+ p += nread;
+ }
+ strbuf_setlen(buf, p - buf->buf);
+ return 0;
+}
+
+off_t fd_copy_bytes(FILE *out, int fd, off_t len)
+{
+ off_t total = 0;
+ while (len) {
+ char buf[4096];
+ ssize_t nread = xread(fd, buf,
+ len < sizeof(buf) ? len : sizeof(buf));
+ if (nread < 0)
+ return error("read error: %s", strerror(errno));
+ if (!nread)
+ return 0;
+ if (out && fwrite(buf, 1, nread, out) != nread)
+ return error("write error: %s", strerror(errno));
+ total += nread;
+ len -= nread;
+ }
+ return total;
+}
diff --git a/vcs-svn/fd_buffer.h b/vcs-svn/fd_buffer.h
new file mode 100644
index 0000000..9434ac3
--- /dev/null
+++ b/vcs-svn/fd_buffer.h
@@ -0,0 +1,19 @@
+#ifndef FD_BUFFER_H
+#define FD_BUFFER_H
+
+#include "strbuf.h"
+
+/* Low-level input helpers. Usually line_buffer is a better choice. */
+
+extern int fd_read_line(struct strbuf *line, int fd);
+extern int fd_read_binary(struct strbuf *buf, size_t len, int fd);
+
+/* returns 0 for end of file */
+extern off_t fd_copy_bytes(FILE *out, int fd, off_t len);
+
+static inline off_t fd_skip_bytes(int fd, off_t len)
+{
+ return fd_copy_bytes(NULL, fd, len);
+}
+
+#endif
--
1.7.2.3
--
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