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.

3 files changed, 21 insertions, 14 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;
 }