X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fread-file.c;h=3bf9b846326e1cdb9f9268c4bec810d47131ad34;hb=b344de996cd51f8a2f2558a3172016b64d99c622;hp=1045b494ccb28c4158304124c0e52099c7319e68;hpb=a42e0dae2fe2bc4d1166d572e8b5b447de9b9873;p=gnulib.git

diff --git a/lib/read-file.c b/lib/read-file.c
index 1045b494c..3bf9b8463 100644
--- a/lib/read-file.c
+++ b/lib/read-file.c
@@ -1,5 +1,5 @@
 /* read-file.c -- read file contents into a string
-   Copyright (C) 2006 Free Software Foundation, Inc.
+   Copyright (C) 2006, 2009-2011 Free Software Foundation, Inc.
    Written by Simon Josefsson and Bruno Haible.
 
    This program is free software; you can redistribute it and/or modify
@@ -20,7 +20,16 @@
 
 #include "read-file.h"
 
-/* Get realloc, free. */
+/* Get fstat.  */
+#include <sys/stat.h>
+
+/* Get ftello.  */
+#include <stdio.h>
+
+/* Get SIZE_MAX.  */
+#include <stdint.h>
+
+/* Get malloc, realloc, free. */
 #include <stdlib.h>
 
 /* Get errno. */
@@ -30,60 +39,104 @@
    and set *LENGTH to the length of the string.  The string is
    zero-terminated, but the terminating zero byte is not counted in
    *LENGTH.  On errors, *LENGTH is undefined, errno preserves the
-   values set by system functions (if any), and NULL is returned. */
+   values set by system functions (if any), and NULL is returned.  */
 char *
-fread_file (FILE * stream, size_t * length)
+fread_file (FILE *stream, size_t *length)
 {
   char *buf = NULL;
-  size_t alloc = 0;
-  size_t size = 0;
-  int save_errno;
-
-  for (;;)
-    {
-      size_t count;
-      size_t requested;
-
-      if (size + BUFSIZ + 1 > alloc)
-	{
-	  char *new_buf;
-
-	  alloc += alloc / 2;
-	  if (alloc < size + BUFSIZ + 1)
-	    alloc = size + BUFSIZ + 1;
-
-	  new_buf = realloc (buf, alloc);
-	  if (!new_buf)
-	    {
-	      save_errno = errno;
-	      break;
-	    }
-
-	  buf = new_buf;
-	}
-
-      requested = alloc - size - 1;
-      count = fread (buf + size, 1, requested, stream);
-      size += count;
-
-      if (count != requested)
-	{
-	  save_errno = errno;
-	  if (ferror (stream))
-	    break;
-	  buf[size] = '\0';
-	  *length = size;
-	  return buf;
-	}
-    }
-
-  free (buf);
-  errno = save_errno;
-  return NULL;
+  size_t alloc = BUFSIZ;
+
+  /* For a regular file, allocate a buffer that has exactly the right
+     size.  This avoids the need to do dynamic reallocations later.  */
+  {
+    struct stat st;
+
+    if (fstat (fileno (stream), &st) >= 0 && S_ISREG (st.st_mode))
+      {
+        off_t pos = ftello (stream);
+
+        if (pos >= 0 && pos < st.st_size)
+          {
+            off_t alloc_off = st.st_size - pos;
+
+            /* '1' below, accounts for the trailing NUL.  */
+            if (SIZE_MAX - 1 < alloc_off)
+              {
+                errno = ENOMEM;
+                return NULL;
+              }
+
+            alloc = alloc_off + 1;
+          }
+      }
+  }
+
+  if (!(buf = malloc (alloc)))
+    return NULL; /* errno is ENOMEM.  */
+
+  {
+    size_t size = 0; /* number of bytes read so far */
+    int save_errno;
+
+    for (;;)
+      {
+        /* This reads 1 more than the size of a regular file
+           so that we get eof immediately.  */
+        size_t requested = alloc - size;
+        size_t count = fread (buf + size, 1, requested, stream);
+        size += count;
+
+        if (count != requested)
+          {
+            save_errno = errno;
+            if (ferror (stream))
+              break;
+
+            /* Shrink the allocated memory if possible.  */
+            if (size < alloc - 1)
+              {
+                char *smaller_buf = realloc (buf, size + 1);
+                if (smaller_buf != NULL)
+                  buf = smaller_buf;
+              }
+
+            buf[size] = '\0';
+            *length = size;
+            return buf;
+          }
+
+        {
+          char *new_buf;
+
+          if (alloc == SIZE_MAX)
+            {
+              save_errno = ENOMEM;
+              break;
+            }
+
+          if (alloc < SIZE_MAX - alloc / 2)
+            alloc = alloc + alloc / 2;
+          else
+            alloc = SIZE_MAX;
+
+          if (!(new_buf = realloc (buf, alloc)))
+            {
+              save_errno = errno;
+              break;
+            }
+
+          buf = new_buf;
+        }
+      }
+
+    free (buf);
+    errno = save_errno;
+    return NULL;
+  }
 }
 
 static char *
-internal_read_file (const char *filename, size_t * length, const char *mode)
+internal_read_file (const char *filename, size_t *length, const char *mode)
 {
   FILE *stream = fopen (filename, mode);
   char *out;
@@ -99,10 +152,10 @@ internal_read_file (const char *filename, size_t * length, const char *mode)
   if (fclose (stream) != 0)
     {
       if (out)
-	{
-	  save_errno = errno;
-	  free (out);
-	}
+        {
+          save_errno = errno;
+          free (out);
+        }
       errno = save_errno;
       return NULL;
     }
@@ -117,7 +170,7 @@ internal_read_file (const char *filename, size_t * length, const char *mode)
    undefined, errno preserves the values set by system functions (if
    any), and NULL is returned.  */
 char *
-read_file (const char *filename, size_t * length)
+read_file (const char *filename, size_t *length)
 {
   return internal_read_file (filename, length, "r");
 }
@@ -130,7 +183,7 @@ read_file (const char *filename, size_t * length)
    preserves the values set by system functions (if any), and NULL is
    returned.  */
 char *
-read_binary_file (const char *filename, size_t * length)
+read_binary_file (const char *filename, size_t *length)
 {
   return internal_read_file (filename, length, "rb");
 }