stdio compat layer for plugins

This is attempt to simplify porting programs to rockbox (as plugins).
Currently this compat layer implements:
fopen(), fclose(), fflush(), fread(), fwrite(), fseek(), fseeko(),
ftell(), ftello(), fgetc(), ungetc(), fputc(), fgets(), clearerr(),
ferror(), feof(), fprintf()

In order to use it you need to include in ported sources
"lib/stdio_compat.h"

Change-Id: I5add615dd19c5af9c767ccbfb1bd5a4e466741cb

apps/plugins/lib/stdio_compat.c

@@ -0,0 +1,231 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ *
+ * Copyright (C) 2013 by Marcin Bukat
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+#include "plugin.h"
+#include "stdio_compat.h"
+
+static _FILE_ __file__[MAX_STDIO_FILES] = {
+    {-1,-1,0},{-1,-1,0},{-1,-1,0},{-1,-1,0},
+    {-1,-1,0},{-1,-1,0},{-1,-1,0},{-1,-1,0}
+};
+
+_FILE_ *_fopen_(const char *path, const char *mode)
+{
+    _FILE_ *f = __file__;
+    int flags = O_RDONLY;
+    int fd = -1;
+    int i;
+
+    /* look for free slot */
+    for (i=0; i<MAX_OPEN_FILES; i++, f++)
+        if (f->fd == -1)
+            break;
+
+    /* no empty slots */
+    if (i == MAX_STDIO_FILES)
+        return NULL;
+
+    if (*mode != 'r')
+    {
+        /* Not read */
+        flags = (O_WRONLY | O_CREAT | O_TRUNC);
+        if (*mode != 'w')
+        {
+            /* Not write (create of append) */
+            flags = (O_WRONLY | O_CREAT | O_APPEND);
+            if (*mode != 'a')
+            {
+                /* Illegal */
+                return NULL;
+            }
+        }
+    }
+
+    if (mode[1] == 'b')
+    {
+        /* Ignore */
+        mode++;
+    }
+
+    if (mode[1] == '+')
+    {
+        /* Read and Write. */
+        flags |= (O_RDONLY | O_WRONLY);
+        flags += (O_RDWR - (O_RDONLY | O_WRONLY));
+    }
+
+
+    fd = rb->open(path, flags);
+
+    if (fd == -1)
+        return NULL;
+
+    /* initialize */
+    f->fd = fd;
+    f->unget_char = -1;
+
+    return f;
+}
+
+int _fflush_(_FILE_ *stream)
+{
+    (void)stream;
+    /* no buffering so we are always in sync */
+    return 0;
+}
+
+size_t _fread_(void *ptr, size_t size, size_t nmemb, _FILE_ *stream)
+{
+    ssize_t ret = rb->read(stream->fd, (char *)ptr, size*nmemb);
+
+    if (ret < (ssize_t)(size*nmemb))
+        stream->error = -1;
+
+    return ret;
+}
+
+size_t _fwrite_(const void *ptr, size_t size, size_t nmemb, _FILE_ *stream)
+{
+    ssize_t ret = rb->write(stream->fd, ptr, size*nmemb);
+
+    if (ret < (ssize_t)(size*nmemb))
+        stream->error = -1;
+
+    return ret;
+}
+
+int _fseek_(_FILE_ *stream, long offset, int whence)
+{
+    return rb->lseek(stream->fd, offset, whence);
+}
+
+long _ftell_(_FILE_ *stream)
+{
+    return rb->lseek(stream->fd, 0, SEEK_CUR);
+}
+
+int _fclose_(_FILE_ *stream)
+{
+    if (stream->fd == -1)
+        return EOF;
+
+    if (rb->close(stream->fd) == -1)
+        return EOF;
+
+    /* free the resource */
+    stream->fd = -1;
+
+    return 0;
+}
+
+int _fgetc_(_FILE_ *stream)
+{
+    unsigned char c;
+
+    if (stream->unget_char != -1)
+    {
+        c = stream->unget_char;
+        stream->unget_char = -1;
+        return c;
+    }
+
+    if ( rb->read(stream->fd, &c, 1) != 1)
+        return EOF;
+
+    return c;
+}
+
+int _ungetc_(int c, _FILE_ *stream)
+{
+    stream->unget_char = c;
+
+    return c;
+}
+
+int _fputc_(int c, _FILE_ *stream)
+{
+    unsigned char cb = c;
+
+    if (rb->write(stream->fd, &cb, 1) != 1)
+        return EOF;
+
+    return cb;
+}
+
+char *_fgets_(char *s, int size, _FILE_ *stream)
+{
+    char *p = s;
+    char c = '\0';
+
+    for (int i=0; i<size; i++)
+    {
+        if ( rb->read(stream->fd, &c, 1) != 1)
+            break;
+
+        *p++ = c;
+
+        if (c == '\n')
+            break;
+    }
+
+    if (p == s)
+        return NULL;
+
+    *p = '\0';
+
+    return s;
+}
+
+void _clearerr_(_FILE_ *stream)
+{
+    if (stream)
+        stream->error = 0;
+}
+
+int _ferror_(_FILE_ *stream)
+{
+    return (stream) ? stream->error : -1;
+}
+
+int _feof_(_FILE_ *stream)
+{
+    int c = _fgetc_(stream);
+
+    if (c != EOF)
+    {
+        _ungetc_(c, stream);
+        return 0;
+    }
+
+    return 0;
+}
+
+int _fprintf_(_FILE_ *stream, const char *format, ...)
+{
+    int len;
+    va_list ap;
+    char buf[256];
+
+    va_start(ap, format);
+    len = rb->vsnprintf(buf, sizeof(buf), format, ap);
+    va_end(ap);
+
+    return _fwrite_(buf, 1, len, stream);
+}