From 8fdcfdb4479dff7a993a25a63253f0e749fd99fe Mon Sep 17 00:00:00 2001
From: Rob Landley <rob@landley.net>
Date: Tue, 3 Sep 2013 17:56:28 -0500
Subject: Introduce libbuf analogous to toybuf but for use by lib/*.c. Change
 readfile() semantics to be able to read into an existing buffer, or malloc
 its own if that's NULL.

---
 lib/lib.c         | 31 +++++++++++++++++++------------
 lib/lib.h         |  2 +-
 lib/xwrap.c       |  2 +-
 main.c            |  2 +-
 toys.h            |  4 ++--
 toys/other/pmap.c |  2 +-
 6 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/lib/lib.c b/lib/lib.c
index 86e99ace..38d9cc21 100644
--- a/lib/lib.c
+++ b/lib/lib.c
@@ -96,11 +96,10 @@ off_t lskip(int fd, off_t offset)
   if (and != -1 && offset >= lseek(fd, offset, SEEK_END)
     && offset+and == lseek(fd, offset+and, SEEK_SET)) return 0;
   else {
-    char buf[4096];
     while (offset>0) {
-      int try = offset>sizeof(buf) ? sizeof(buf) : offset, or;
+      int try = offset>sizeof(libbuf) ? sizeof(libbuf) : offset, or;
 
-      or = readall(fd, buf, try);
+      or = readall(fd, libbuf, try);
       if (or < 0) perror_msg("lskip to %lld", (long long)offset);
       else offset -= try;
       if (or < try) break;
@@ -259,20 +258,28 @@ off_t fdlength(int fd)
   return base;
 }
 
-// Read contents of file as a single freshly allocated nul-terminated string.
-char *readfile(char *name)
+// Read contents of file as a single nul-terminated string.
+// malloc new one if buf=len=0
+char *readfile(char *name, char *buf, off_t len)
 {
-  off_t len;
   int fd;
-  char *buf;
 
   fd = open(name, O_RDONLY);
   if (fd == -1) return 0;
-  len = fdlength(fd);
-  // proc files don't report a length, so try 1 page minimum.
-  if (len<4096) len = 4095;
-  buf = xmalloc(len+1);
-  buf[readall(fd, buf, len)] = 0;
+
+  if (len<1) {
+    len = fdlength(fd);
+    // proc files don't report a length, so try 1 page minimum.
+    if (len<4096) len = 4096;
+  }
+  if (!buf) buf = xmalloc(len+1);
+
+  len = readall(fd, buf, len-1);
+  close(fd);
+  if (len<0) {
+    free(buf);
+    buf = 0;
+  } else buf[len] = 0;
 
   return buf;
 }
diff --git a/lib/lib.h b/lib/lib.h
index 14e14e91..26465ad4 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -135,7 +135,7 @@ ssize_t readall(int fd, void *buf, size_t len);
 ssize_t writeall(int fd, void *buf, size_t len);
 off_t lskip(int fd, off_t offset);
 struct string_list **splitpath(char *path, struct string_list **list);
-char *readfile(char *name);
+char *readfile(char *name, char *buf, off_t len);
 void msleep(long miliseconds);
 int64_t peek(void *ptr, int size);
 void poke(void *ptr, uint64_t val, int size);
diff --git a/lib/xwrap.c b/lib/xwrap.c
index 2b0690f3..90c4d86a 100644
--- a/lib/xwrap.c
+++ b/lib/xwrap.c
@@ -425,7 +425,7 @@ char *xreadlink(char *name)
 
 char *xreadfile(char *name)
 {
-  char *buf = readfile(name);
+  char *buf = readfile(name, 0, 0);
   if (!buf) perror_exit("xreadfile %s", name);
   return buf;
 }
diff --git a/main.c b/main.c
index dd985b84..53f670d2 100644
--- a/main.c
+++ b/main.c
@@ -20,7 +20,7 @@ struct toy_list toy_list[] = {
 
 struct toy_context toys;
 union global_union this;
-char toybuf[4096];
+char toybuf[4096], libbuf[4096];
 
 struct toy_list *toy_find(char *name)
 {
diff --git a/toys.h b/toys.h
index c810123a..b7acc270 100644
--- a/toys.h
+++ b/toys.h
@@ -113,9 +113,9 @@ extern struct toy_context {
   jmp_buf *rebound;        // longjmp here instead of exit when do_rebound set
 } toys;
 
-// One big temporary buffer, for use by commands (not library functions).
+// Two big temporary buffers: one for use by commands, one for library functions
 
-extern char toybuf[4096];
+extern char toybuf[4096], libbuf[4096];
 
 extern char **environ;
 
diff --git a/toys/other/pmap.c b/toys/other/pmap.c
index 012280dd..1cc04220 100644
--- a/toys/other/pmap.c
+++ b/toys/other/pmap.c
@@ -35,7 +35,7 @@ void pmap_main(void)
     int count, xx = 0;
 
     snprintf(toybuf, sizeof(toybuf), "/proc/%u/cmdline", pid);
-    line = readfile(toybuf);
+    line = readfile(toybuf, 0, 0);
     if (!line) error_msg("No %lu", (long)pid);
     xprintf("%u: %s\n", (int)pid, line);
     free(line);
-- 
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