Add write_or_die(), a helper function

The little helper write_or_die() won't come back with bad news about
full disks or broken pipes.  It either succeeds or terminates the
program, making additional error handling unnecessary.

This patch adds the new function and uses it to replace two similar
ones (the one in tar-tree originally has been copied from cat-file
btw.).  I chose to add the fd parameter which both lacked to make
write_or_die() just as flexible as write() and thus suitable for
lib-ification.

There is a regression: error messages emitted by this function don't
show the program name, while the replaced two functions did.  That's
acceptable, I think; a lot of other functions do the same.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Makefile

@@ -248,6 +248,7 @@ LIB_OBJS = \
 	server-info.o setup.o sha1_file.o sha1_name.o strbuf.o \
 	tag.o tree.o usage.o config.o environment.o ctype.o copy.o \
 	fetch-clone.o revision.o pager.o tree-walk.o xdiff-interface.o \
+	write_or_die.o \
 	alloc.o merge-file.o path-list.o help.o unpack-trees.o $(DIFF_OBJS)
 
 BUILTIN_OBJS = \

builtin-cat-file.c

@@ -9,23 +9,6 @@
 #include "tree.h"
 #include "builtin.h"
 
-static void flush_buffer(const char *buf, unsigned long size)
-{
-	while (size > 0) {
-		long ret = xwrite(1, buf, size);
-		if (ret < 0) {
-			/* Ignore epipe */
-			if (errno == EPIPE)
-				break;
-			die("git-cat-file: %s", strerror(errno));
-		} else if (!ret) {
-			die("git-cat-file: disk full?");
-		}
-		size -= ret;
-		buf += ret;
-	}
-}
-
 static void pprint_tag(const unsigned char *sha1, const char *buf, unsigned long size)
 {
 	/* the parser in tag.c is useless here. */
@@ -42,7 +25,7 @@ static void pprint_tag(const unsigned char *sha1, const char *buf, unsigned long
 			/* Found the tagger line.  Copy out the contents
 			 * of the buffer so far.
 			 */
-			flush_buffer(buf, cp - buf);
+			write_or_die(1, buf, cp - buf);
 
 			/*
 			 * Do something intelligent, like pretty-printing
@@ -61,18 +44,18 @@ static void pprint_tag(const unsigned char *sha1, const char *buf, unsigned long
 						sp++;
 					if (sp == cp) {
 						/* give up */
-						flush_buffer(tagger,
+						write_or_die(1, tagger,
 							     cp - tagger);
 						break;
 					}
 					while (sp < cp &&
 					       !('0' <= *sp && *sp <= '9'))
 						sp++;
-					flush_buffer(tagger, sp - tagger);
+					write_or_die(1, tagger, sp - tagger);
 					date = strtoul(sp, &ep, 10);
 					tz = strtol(ep, NULL, 10);
 					sp = show_date(date, tz);
-					flush_buffer(sp, strlen(sp));
+					write_or_die(1, sp, strlen(sp));
 					xwrite(1, "\n", 1);
 					break;
 				}
@@ -90,7 +73,7 @@ static void pprint_tag(const unsigned char *sha1, const char *buf, unsigned long
 	 * remainder as is.
 	 */
 	if (cp < endp)
-		flush_buffer(cp, endp - cp);
+		write_or_die(1, cp, endp - cp);
 }
 
 int cmd_cat_file(int argc, const char **argv, const char *prefix)
@@ -162,6 +145,6 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix)
 	if (!buf)
 		die("git-cat-file %s: bad file", argv[2]);
 
-	flush_buffer(buf, size);
+	write_or_die(1, buf, size);
 	return 0;
 }

builtin-tar-tree.c

@@ -22,30 +22,11 @@ static unsigned long offset;
 static time_t archive_time;
 static int tar_umask;
 
-/* tries hard to write, either succeeds or dies in the attempt */
-static void reliable_write(const void *data, unsigned long size)
-{
-	const char *buf = data;
-
-	while (size > 0) {
-		long ret = xwrite(1, buf, size);
-		if (ret < 0) {
-			if (errno == EPIPE)
-				exit(0);
-			die("git-tar-tree: %s", strerror(errno));
-		} else if (!ret) {
-			die("git-tar-tree: disk full?");
-		}
-		size -= ret;
-		buf += ret;
-	}
-}
-
 /* writes out the whole block, but only if it is full */
 static void write_if_needed(void)
 {
 	if (offset == BLOCKSIZE) {
-		reliable_write(block, BLOCKSIZE);
+		write_or_die(1, block, BLOCKSIZE);
 		offset = 0;
 	}
 }
@@ -70,7 +51,7 @@ static void write_blocked(const void *data, unsigned long size)
 		write_if_needed();
 	}
 	while (size >= BLOCKSIZE) {
-		reliable_write(buf, BLOCKSIZE);
+		write_or_die(1, buf, BLOCKSIZE);
 		size -= BLOCKSIZE;
 		buf += BLOCKSIZE;
 	}
@@ -94,10 +75,10 @@ static void write_trailer(void)
 {
 	int tail = BLOCKSIZE - offset;
 	memset(block + offset, 0, tail);
-	reliable_write(block, BLOCKSIZE);
+	write_or_die(1, block, BLOCKSIZE);
 	if (tail < 2 * RECORDSIZE) {
 		memset(block, 0, offset);
-		reliable_write(block, BLOCKSIZE);
+		write_or_die(1, block, BLOCKSIZE);
 	}
 }
 

cache.h

@@ -388,6 +388,7 @@ extern char git_default_name[MAX_GITNAME];
 extern char git_commit_encoding[MAX_ENCODING_LENGTH];
 
 extern int copy_fd(int ifd, int ofd);
+extern void write_or_die(int fd, const void *buf, size_t count);
 
 /* Finish off pack transfer receiving end */
 extern int receive_unpack_pack(int fd[2], const char *me, int quiet, int);

write_or_die.c

@@ -0,0 +1,20 @@
+#include "cache.h"
+
+void write_or_die(int fd, const void *buf, size_t count)
+{
+	const char *p = buf;
+	ssize_t written;
+
+	while (count > 0) {
+		written = xwrite(fd, p, count);
+		if (written == 0)
+			die("disk full?");
+		else if (written < 0) {
+			if (errno == EPIPE)
+				exit(0);
+			die("write error (%s)", strerror(errno));
+		}
+		count -= written;
+		p += written;
+	}
+}