Changeset 1c7f381 in mainline

Timestamp:

2018-01-22T20:12:00Z (6 years ago)

Author:

Jiří Zárevúcky <zarevucky.jiri@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

e0f47f5

Parents:

df2e5514

Message:

Add nonstandard ftell64() and fseek64().

Currently, the C standard does not define any functions that can access file
offset with full 64-bit range. Standard ftell()/fseek() are nonportable on files
over 2 GB, while fgetpos()/fsetpos() can work with arbitrary length file, but
keep the position opaque, and no cannot be used for seeks to known numerical
offsets.

POSIX defines ftello()/fseeko(), which _can_ be 64-bit, but aren't guaranteed
to be by the standard, and come with additional baggage. Also, the naming
is rather awkward.

In short, there is no portable interface for this functionality, so
a pair of nonstandard functions is an adequate answer for this.

Location:

uspace/lib/c

Files:

• generic/io/io.c (modified) (3 diffs)
• include/stdio.h (modified) (1 diff)

uspace/lib/c/generic/io/io.c

@@ -799 +799 @@
 }
 
-int fseek(FILE *stream, long offset, int whence)
+int fseek64(FILE *stream, off64_t offset, int whence)
 {
         errno_t rc;
@@ -837 +837 @@
 }
 
-long ftell(FILE *stream)
-{
-        /* The native position is too large for the C99-ish interface. */
-        if (stream->pos - stream->ungetc_chars > LONG_MAX)
-                return EOF;
-
+off64_t ftell64(FILE *stream)
+{
         if (stream->error)
                 return EOF;
@@ -853 +849 @@
 
         return stream->pos - stream->ungetc_chars;
+}
+
+int fseek(FILE *stream, long offset, int whence)
+{
+        return fseek64(stream, offset, whence);
+}
+
+long ftell(FILE *stream)
+{
+        off64_t off = ftell64(stream);
+
+        /* The native position is too large for the C99-ish interface. */
+        if (off > LONG_MAX)
+                return EOF;
+
+        return off;
 }
 

uspace/lib/c/include/stdio.h

@@ -158 +158 @@
 extern char *gets(char *, size_t);
 
+#include <offset.h>
+
+extern int fseek64(FILE *, off64_t, int);
+extern off64_t ftell64(FILE *);
+
 #endif