From 3dad2125b9048fdc3790d3e7c4770f7174be889c Mon Sep 17 00:00:00 2001
From: "Markus F.X.J. Oberhumer" <markus@oberhumer.com>
Date: Thu, 15 Apr 2021 18:37:32 +0200
Subject: util: add safe_read_all() and safe_write_all() functions.

---
 bar.c   | 12 +-----------
 spawn.c |  4 ++--
 util.c  | 35 +++++++++++++++++++++++++++++++++++
 util.h  | 10 ++++++++++
 4 files changed, 48 insertions(+), 13 deletions(-)

diff --git a/bar.c b/bar.c
index 67f5d6e..33127f8 100644
--- a/bar.c
+++ b/bar.c
@@ -58,17 +58,7 @@ static int bfs_bar_getsize(struct bfs_bar *bar) {
 /** Async Signal Safe puts(). */
 static int ass_puts(int fd, const char *str) {
 	size_t len = strlen(str);
-
-	while (len > 0) {
-		ssize_t ret = safe_write(fd, str, len);
-		if (ret <= 0) {
-			return -1;
-		}
-		str += ret;
-		len -= ret;
-	}
-
-	return 0;
+	return safe_write_all(fd, str, len) == (ssize_t)len ? 0 : -1;
 }
 
 /** Number of decimal digits needed for terminal sizes. */
diff --git a/spawn.c b/spawn.c
index 5878122..0a260dc 100644
--- a/spawn.c
+++ b/spawn.c
@@ -191,7 +191,7 @@ fail:
 
 	// In case of write error parent will still see that we exited
 	// unsuccessfully, but won't know why.
-	safe_write(pipefd[1], &error, sizeof(error));
+	(void) safe_write_all(pipefd[1], &error, sizeof(error));
 
 	close(pipefd[1]);
 	_Exit(127);
@@ -221,7 +221,7 @@ pid_t bfs_spawn(const char *exe, const struct bfs_spawn *ctx, char **argv, char
 	// Parent
 	close(pipefd[1]);
 
-	ssize_t nbytes = safe_read(pipefd[0], &error, sizeof(error));
+	ssize_t nbytes = safe_read_all(pipefd[0], &error, sizeof(error));
 	close(pipefd[0]);
 	if (nbytes == sizeof(error)) {
 		int wstatus;
diff --git a/util.c b/util.c
index 611d4b5..00f5b78 100644
--- a/util.c
+++ b/util.c
@@ -379,6 +379,23 @@ ssize_t safe_read(int fd, void *buf, size_t nbytes) {
 	}
 }
 
+ssize_t safe_read_all(int fd, void *buf, size_t nbytes) {
+	size_t count = 0;
+	for (;;) {
+		ssize_t ret = read(fd, (char *)buf + count, nbytes - count);
+		if (ret < 0 && errno == EINTR) {
+			continue;
+		}
+		if (ret < 0) {
+			return ret; // always return error < 0
+		}
+		count += ret;
+		if (ret == 0 || count == nbytes) { // EOF or success
+			return count;
+		}
+	}
+}
+
 ssize_t safe_write(int fd, const void *buf, size_t nbytes) {
 	for (;;) {
 		ssize_t ret = write(fd, buf, nbytes);
@@ -388,3 +405,21 @@ ssize_t safe_write(int fd, const void *buf, size_t nbytes) {
 		return ret;
 	}
 }
+
+ssize_t safe_write_all(int fd, const void *buf, size_t nbytes)
+{
+	size_t count = 0;
+	for (;;) {
+		ssize_t ret = write(fd, (const char *)buf + count, nbytes - count);
+		if (ret < 0 && errno == EINTR) {
+			continue;
+		}
+		if (ret < 0) {
+			return ret; // always return error < 0
+		}
+		count += ret;
+		if (ret == 0 || count == nbytes) { // EOF (should never happen with write) or success
+			return count;
+		}
+	}
+}
diff --git a/util.h b/util.h
index ef67566..7293d50 100644
--- a/util.h
+++ b/util.h
@@ -230,9 +230,19 @@ int bfs_minor(dev_t dev);
  */
 ssize_t safe_read(int fd, void *buf, size_t nbytes);
 
+/**
+ * A safe version of read() that handles interrupted system calls and partial reads.
+ */
+ssize_t safe_read_all(int fd, void *buf, size_t nbytes);
+
 /**
  * A safe version of write() that handles interrupted system calls.
  */
 ssize_t safe_write(int fd, const void *buf, size_t nbytes);
 
+/**
+ * A safe version of write() that handles interrupted system calls and partial writes.
+ */
+ssize_t safe_write_all(int fd, const void *buf, size_t nbytes);
+
 #endif // BFS_UTIL_H
-- 
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