From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sun, 17 Jul 2022 18:34:22 +0000 (+0100)
Subject: prefork-interp: wip use stdio
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?a=commitdiff_plain;h=3c04116f7323ef5ac4ee7103c9132482b54b82f0;p=chiark-utils.git

prefork-interp: wip use stdio

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---

diff --git a/cprogs/prefork-interp.c b/cprogs/prefork-interp.c
index de63b42..fdc5da9 100644
--- a/cprogs/prefork-interp.c
+++ b/cprogs/prefork-interp.c
@@ -181,7 +181,9 @@ static void prepare_message(size_t *len, char **buf) {
     prepare_string(len, buf, s);
 }
 
-static void send_fd(int via_fd, int payload_fd) {
+static void send_fd(FILE *call_sock, int payload_fd) {
+  int via_fd = fileno(call_sock);
+
   union {
     struct cmsghdr align;
     char buf[CMSG_SPACE(sizeof(payload_fd))];
@@ -222,12 +224,12 @@ static void send_fd(int via_fd, int payload_fd) {
   }
 }
 
-static void send_request(int call_fd) {
+static void send_request(FILE *call_sock) {
   // Sending these first makes it easier for the script to
   // use buffered IO for the message.
-  send_fd(call_fd, 0);
-  send_fd(call_fd, 1);
-  send_fd(call_fd, 2);
+  send_fd(call_sock, 0);
+  send_fd(call_sock, 1);
+  send_fd(call_sock, 2);
 
   size_t len = 4;
   prepare_message(&len, 0);
@@ -238,25 +240,28 @@ static void send_request(int call_fd) {
   prepare_message(0, &p);
   assert(p == m + len);
 
-  p = m;
-  while (len) {
-    ssize_t r = write(call_fd, p, len);
-    if (r==-1) {
-      if (errno == EINTR) continue;
-      diee("write request");
-    }
-    assert(r <= len);
-    assert(r > 0);
-    len -= r;
-    p += r;
-  }
+  ssize_t sr = fwrite(p, len, 1, call_sock);
+  if (sr != 1) diee("write request");
+}
+
+static FILE *call_sock_from_fd(int fd) {
+  int r;
+
+  FILE *call_sock = fdopen(fd, "r+");
+  if (!call_sock) diee("fdopen socket");
+
+  r = setvbuf(call_sock, 0, _IONBF, 0);
+  if (r) die("setvbuf socket");
+
+  return call_sock;
 }
 
-// Returns: call(client-end) fd, or -1 to mean "is garbage"
+// Returns: call(client-end), or 0 to mean "is garbage"
 // find_socket_path must have been called
-static int connect_existing(void) {
+static FILE *connect_existing(void) {
   int r;
   int fd = -1;
+  FILE *call_sock;
 
   fd = socket(AF_UNIX, SOCK_STREAM, 0);
   if (fd==-1) diee("socket() for client");
@@ -268,27 +273,26 @@ static int connect_existing(void) {
     diee("connect() %s", socket_path);
   }
 
-  for (;;) {
-    char ack;
-    size_t sr = read(fd, &ack, 1);
-    if (sr == -1) {
-      if (errno==ECONNRESET) goto x_garbage;
-      if (errno==EINTR) continue;
-      diee("read() ack byte");
-    }
-    if (sr == 0) { goto x_garbage; }
-    if (ack != '\n') die("got ack byte 0x%02x, not '\n'", ack);
-    break;
+  call_sock = call_sock_from_fd(fd);
+  fd = -1;
+
+  char ack;
+  size_t sr = fread(&ack, sizeof(ack), 1, call_sock);
+  if (sr != 1) {
+    if (feof(call_sock) || errno==ECONNRESET) goto x_garbage;
+    diee("read() ack byte");
   }
+  if (ack != '\n') die("got ack byte 0x%02x, not '\n'", ack);
 
   // We're committed now, send the request (or bail out)
-  send_request(fd);
+  send_request(call_sock);
 
-  return fd;
+  return call_sock;
 
  x_garbage:
+  fclose(call_sock);
   if (fd >= 0) close(fd);
-  return -1;
+  return 0;
 }
 
 static __attribute__((noreturn))
@@ -310,15 +314,15 @@ void become_setup(int sfd, int fake_pair[2]) {
   diee("execute %s", executor_argv[0]);
 }
 
-static int connect_or_spawn(void) {
+static FILE *connect_or_spawn(void) {
   int r;
 
-  int fd = connect_existing();
-  if (fd >= 0) return fd;
+  FILE *call_sock = connect_existing();
+  if (call_sock) return call_sock;
 
   int lockfd = acquire_lock();
-  fd = connect_existing();
-  if (fd >= 0) { close(lockfd); return fd; }
+  call_sock = connect_existing();
+  if (call_sock) { close(lockfd); return call_sock; }
 
   // We must start a fresh one, and we hold the lock
 
@@ -357,7 +361,7 @@ static int connect_or_spawn(void) {
   if (status != 0) propagate_exit_status(status, "invocation");
 
   close(lockfd);
-  return fake_pair[0];
+  return call_sock_from_fd(fake_pair[0]);
 }
 
 static void make_executor_argv(const char *const *argv) {
@@ -396,5 +400,5 @@ int main(int argc_unused, const char *const *argv) {
   assert(strlen(socket_path) <= sizeof(sun.sun_path));
   strncpy(sun.sun_path, socket_path, sizeof(sun.sun_path));
 
-  int call_fd = connect_or_spawn();
+  FILE *call_sock = connect_or_spawn();
 }