[lib][stdio] implement a real FILE backing stdio descriptors

Allows different implementations of FILE handling to be provided.
Make lib/debug provide the default implementation for
stdin/stdout/stderr.

Change-Id: Icd9d30ac44884648603e91cfca856912bca1c0d3
Signed-off-by: Dima Zavin <dima@android.com>

3 files changed, 60 insertions, 18 deletions

diff --git a/include/stdio.h b/include/stdio.h
index 75cd3723..ce9c548b 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -29,13 +29,19 @@
 
 __BEGIN_CDECLS
 
-/* fake FILE struct */
 typedef struct FILE {
+	void *ctx;
+	int (*fputc)(void *ctx, int c);
+	int (*fputs)(void *ctx, const char *s);
+	int (*fgetc)(void *ctx);
+	int (*vfprintf)(void *ctx, const char *fmt, va_list ap);
 } FILE;
 
-#define stdin ((FILE *)1)
-#define stdout ((FILE *)2)
-#define stderr ((FILE *)3)
+extern FILE __stdio_FILEs[];
+
+#define stdin  (&__stdio_FILEs[0])
+#define stdout (&__stdio_FILEs[1])
+#define stderr (&__stdio_FILEs[2])
 
 FILE *fopen(const char *filename, const char *mode);
 int fclose(FILE *stream);
diff --git a/lib/debug/debug.c b/lib/debug/debug.c
index bf2777e8..761195cf 100644
--- a/lib/debug/debug.c
+++ b/lib/debug/debug.c
@@ -59,6 +59,49 @@ void _panic(void *caller, const char *fmt, ...)
 	halt();
 }
 
+static int __debug_stdio_fputc(void *ctx, int c)
+{
+	_dputc(c);
+	return 0;
+}
+
+static int __debug_stdio_fputs(void *ctx, const char *s)
+{
+	return _dputs(s);
+}
+
+static int __debug_stdio_fgetc(void *ctx)
+{
+	char c;
+	int err;
+
+	err = platform_dgetc(&c, true);
+	if (err < 0)
+		return err;
+	return (unsigned char)c;
+}
+
+static int __debug_stdio_vfprintf(void *ctx, const char *fmt, va_list ap)
+{
+	return _dvprintf(fmt, ap);
+}
+
+#define DEFINE_STDIO_DESC(id)						\
+	[(id)]	= {							\
+		.ctx		= &__stdio_FILEs[(id)],			\
+		.fputc		= __debug_stdio_fputc,			\
+		.fputs		= __debug_stdio_fputs,			\
+		.fgetc		= __debug_stdio_fgetc,			\
+		.vfprintf	= __debug_stdio_vfprintf,		\
+	}
+
+FILE __stdio_FILEs[3] = {
+	DEFINE_STDIO_DESC(0), /* stdin */
+	DEFINE_STDIO_DESC(1), /* stdout */
+	DEFINE_STDIO_DESC(2), /* stderr */
+};
+#undef DEFINE_STDIO_DESC
+
 #if !DISABLE_DEBUG_OUTPUT
 
 int _dputs(const char *str)
diff --git a/lib/libc/stdio.c b/lib/libc/stdio.c
index a65b30b5..698700b8 100644
--- a/lib/libc/stdio.c
+++ b/lib/libc/stdio.c
@@ -28,8 +28,7 @@
 
 int fputc(int c, FILE *fp)
 {
-	_dputc(c);
-	return 0;
+	return fp->fputc(fp->ctx, c);
 }
 
 int putchar(int c)
@@ -39,27 +38,20 @@ int putchar(int c)
 
 int puts(const char *str)
 {
-	int err = _dputs(str);
+	int err = fputs(str, stdout);
 	if (err >= 0)
-		_dputc('\n');
-
+		err = fputc('\n', stdout);
 	return err;
 }
 
 int fputs(const char *s, FILE *fp)
 {
-	return _dputs(s);
+	return fp->fputs(fp->ctx, s);
 }
 
 int getc(FILE *fp)
 {
-	char c;
-
-	int err = platform_dgetc(&c, true);
-	if (err < 0)
-		return err;
-
-	return (unsigned char)c;
+	return fp->fgetc(fp->ctx);
 }
 
 int getchar(void)
@@ -70,10 +62,11 @@ int getchar(void)
 int _printf(const char *fmt, ...)
 {
 	int err;
+	FILE *fp = stdout;
 
 	va_list ap;
 	va_start(ap, fmt);
-	err = _dvprintf(fmt, ap);
+	err = fp->vfprintf(fp->ctx, fmt, ap);
 	va_end(ap);
 
 	return err;