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authorJeff King <peff@peff.net>2016-06-17 23:38:47 (GMT)
committerJunio C Hamano <gitster@pobox.com>2016-06-18 00:03:56 (GMT)
commit96335bcf4d64c29add3692fb41671190123cf44e (patch)
tree079533fb3d349577395d95f0047e13a73f9b70a4 /run-command.c
parent4322353bfb53a83e6657af50603d3521ee9d7d0c (diff)
downloadgit-96335bcf4d64c29add3692fb41671190123cf44e.zip
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run-command: add pipe_command helper
We already have capture_command(), which captures the stdout of a command in a way that avoids deadlocks. But sometimes we need to do more I/O, like capturing stderr as well, or sending data to stdin. It's easy to write code that deadlocks racily in these situations depending on how fast the command reads its input, or in which order it writes its output. Let's give callers an easy interface for doing this the right way, similar to what capture_command() did for the simple case. The whole thing is backed by a generic poll() loop that can feed an arbitrary number of buffers to descriptors, and fill an arbitrary number of strbufs from other descriptors. This seems like overkill, but the resulting code is actually a bit cleaner than just handling the three descriptors (because the output code for stdout/stderr is effectively duplicated, so being able to loop is a benefit). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'run-command.c')
-rw-r--r--run-command.c152
1 files changed, 147 insertions, 5 deletions
diff --git a/run-command.c b/run-command.c
index af0c8a1..33bc63a 100644
--- a/run-command.c
+++ b/run-command.c
@@ -864,19 +864,161 @@ int run_hook_le(const char *const *env, const char *name, ...)
return ret;
}
-int capture_command(struct child_process *cmd, struct strbuf *buf, size_t hint)
+struct io_pump {
+ /* initialized by caller */
+ int fd;
+ int type; /* POLLOUT or POLLIN */
+ union {
+ struct {
+ const char *buf;
+ size_t len;
+ } out;
+ struct {
+ struct strbuf *buf;
+ size_t hint;
+ } in;
+ } u;
+
+ /* returned by pump_io */
+ int error; /* 0 for success, otherwise errno */
+
+ /* internal use */
+ struct pollfd *pfd;
+};
+
+static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
+{
+ int pollsize = 0;
+ int i;
+
+ for (i = 0; i < nr; i++) {
+ struct io_pump *io = &slots[i];
+ if (io->fd < 0)
+ continue;
+ pfd[pollsize].fd = io->fd;
+ pfd[pollsize].events = io->type;
+ io->pfd = &pfd[pollsize++];
+ }
+
+ if (!pollsize)
+ return 0;
+
+ if (poll(pfd, pollsize, -1) < 0) {
+ if (errno == EINTR)
+ return 1;
+ die_errno("poll failed");
+ }
+
+ for (i = 0; i < nr; i++) {
+ struct io_pump *io = &slots[i];
+
+ if (io->fd < 0)
+ continue;
+
+ if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
+ continue;
+
+ if (io->type == POLLOUT) {
+ ssize_t len = xwrite(io->fd,
+ io->u.out.buf, io->u.out.len);
+ if (len < 0) {
+ io->error = errno;
+ close(io->fd);
+ io->fd = -1;
+ } else {
+ io->u.out.buf += len;
+ io->u.out.len -= len;
+ if (!io->u.out.len) {
+ close(io->fd);
+ io->fd = -1;
+ }
+ }
+ }
+
+ if (io->type == POLLIN) {
+ ssize_t len = strbuf_read_once(io->u.in.buf,
+ io->fd, io->u.in.hint);
+ if (len < 0)
+ io->error = errno;
+ if (len <= 0) {
+ close(io->fd);
+ io->fd = -1;
+ }
+ }
+ }
+
+ return 1;
+}
+
+static int pump_io(struct io_pump *slots, int nr)
+{
+ struct pollfd *pfd;
+ int i;
+
+ for (i = 0; i < nr; i++)
+ slots[i].error = 0;
+
+ ALLOC_ARRAY(pfd, nr);
+ while (pump_io_round(slots, nr, pfd))
+ ; /* nothing */
+ free(pfd);
+
+ /* There may be multiple errno values, so just pick the first. */
+ for (i = 0; i < nr; i++) {
+ if (slots[i].error) {
+ errno = slots[i].error;
+ return -1;
+ }
+ }
+ return 0;
+}
+
+
+int pipe_command(struct child_process *cmd,
+ const char *in, size_t in_len,
+ struct strbuf *out, size_t out_hint,
+ struct strbuf *err, size_t err_hint)
{
- cmd->out = -1;
+ struct io_pump io[3];
+ int nr = 0;
+
+ if (in)
+ cmd->in = -1;
+ if (out)
+ cmd->out = -1;
+ if (err)
+ cmd->err = -1;
+
if (start_command(cmd) < 0)
return -1;
- if (strbuf_read(buf, cmd->out, hint) < 0) {
- close(cmd->out);
+ if (in) {
+ io[nr].fd = cmd->in;
+ io[nr].type = POLLOUT;
+ io[nr].u.out.buf = in;
+ io[nr].u.out.len = in_len;
+ nr++;
+ }
+ if (out) {
+ io[nr].fd = cmd->out;
+ io[nr].type = POLLIN;
+ io[nr].u.in.buf = out;
+ io[nr].u.in.hint = out_hint;
+ nr++;
+ }
+ if (err) {
+ io[nr].fd = cmd->err;
+ io[nr].type = POLLIN;
+ io[nr].u.in.buf = err;
+ io[nr].u.in.hint = err_hint;
+ nr++;
+ }
+
+ if (pump_io(io, nr) < 0) {
finish_command(cmd); /* throw away exit code */
return -1;
}
- close(cmd->out);
return finish_command(cmd);
}