Add fz_output_as_stream

This provides a way for some output streams to also be read, a feature
needed for the sake of document signing. Currently this is supported only
for file output.

4 files changed, 51 insertions, 2 deletions

diff --git a/include/mupdf/fitz/output.h b/include/mupdf/fitz/output.h
index 0425e353..2530be47 100644
--- a/include/mupdf/fitz/output.h
+++ b/include/mupdf/fitz/output.h
@@ -5,6 +5,7 @@
 #include "mupdf/fitz/context.h"
 #include "mupdf/fitz/buffer.h"
 #include "mupdf/fitz/string-util.h"
+#include "mupdf/fitz/stream.h"
 
 /*
 	Generic output streams - generalise between outputting to a file,
@@ -62,6 +63,13 @@ typedef void (fz_output_close_fn)(fz_context *ctx, void *state);
 */
 typedef void (fz_output_drop_fn)(fz_context *ctx, void *state);
 
+/*
+	fz_stream_from_output_fn: A function type for use when implementing
+	fz_outputs. The supplied function of this type is called
+	when the fz_stream_from_output is called.
+*/
+typedef fz_stream *(fz_stream_from_output_fn)(fz_context *ctx, void *state);
+
 
 struct fz_output_s
 {
@@ -71,6 +79,7 @@ struct fz_output_s
 	fz_output_tell_fn *tell;
 	fz_output_close_fn *close;
 	fz_output_drop_fn *drop;
+	fz_stream_from_output_fn *as_stream;
 };
 
 /*
@@ -172,6 +181,16 @@ void fz_close_output(fz_context *, fz_output *);
 void fz_drop_output(fz_context *, fz_output *);
 
 /*
+	fz_stream_from_output: obtain the fz_output in the form of a fz_stream
+
+	This allows data to be read back from some forms of fz_output object.
+	When finished reading, the fz_stream should be released by calling
+	fz_drop_stream. Until the fz_stream is dropped, no further operations
+	should be performed on the fz_output object.
+*/
+fz_stream *fz_stream_from_output(fz_context *, fz_output *);
+
+/*
 	fz_write_data: Write data to output.
 
 	data: Pointer to data to write.
diff --git a/source/fitz/fitz-imp.h b/source/fitz/fitz-imp.h
index 41c905e4..9740213d 100644
--- a/source/fitz/fitz-imp.h
+++ b/source/fitz/fitz-imp.h
@@ -3,6 +3,8 @@
 
 #include "mupdf/fitz.h"
 
+#include <stdio.h>
+
 struct fz_buffer_s
 {
 	int refs;
@@ -91,6 +93,8 @@ void fz_new_output_context(fz_context *ctx);
 void fz_drop_output_context(fz_context *ctx);
 fz_output_context *fz_keep_output_context(fz_context *ctx);
 
+fz_stream *fz_open_file_ptr_no_close(fz_context *ctx, FILE *file);
+
 #if defined(MEMENTO) || !defined(NDEBUG)
 #define FITZ_DEBUG_LOCKING
 #endif
diff --git a/source/fitz/output.c b/source/fitz/output.c
index 4c6aa6b4..18791603 100644
--- a/source/fitz/output.c
+++ b/source/fitz/output.c
@@ -158,6 +158,14 @@ file_drop(fz_context *ctx, void *opaque)
 		fz_warn(ctx, "cannot fclose: %s", strerror(errno));
 }
 
+static fz_stream *
+file_as_stream(fz_context *ctx, void *opaque)
+{
+	FILE *file = opaque;
+	fflush(file);
+	return fz_open_file_ptr_no_close(ctx, file);
+};
+
 fz_output *
 fz_new_output(fz_context *ctx, void *state, fz_output_write_fn *write, fz_output_close_fn *close, fz_output_drop_fn *drop)
 {
@@ -197,7 +205,7 @@ fz_new_output_with_path(fz_context *ctx, const char *filename, int append)
 			if (errno != ENOENT)
 				fz_throw(ctx, FZ_ERROR_GENERIC, "cannot remove file '%s': %s", filename, strerror(errno));
 	}
-	file = fz_fopen_utf8(filename, append ? "ab" : "wb");
+	file = fz_fopen_utf8(filename, "rb+");
 #else
 	/* Ensure we create a brand new file. We don't want to clobber our old file. */
 	if (!append)
@@ -206,7 +214,7 @@ fz_new_output_with_path(fz_context *ctx, const char *filename, int append)
 			if (errno != ENOENT)
 				fz_throw(ctx, FZ_ERROR_GENERIC, "cannot remove file '%s': %s", filename, strerror(errno));
 	}
-	file = fopen(filename, append ? "ab" : "wb");
+	file = fopen(filename, "rb+");
 #endif
 	if (!file)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "cannot open file '%s': %s", filename, strerror(errno));
@@ -214,6 +222,7 @@ fz_new_output_with_path(fz_context *ctx, const char *filename, int append)
 	out = fz_new_output(ctx, file, file_write, NULL, file_drop);
 	out->seek = file_seek;
 	out->tell = file_tell;
+	out->as_stream = file_as_stream;
 
 	return out;
 }
@@ -293,6 +302,15 @@ fz_tell_output(fz_context *ctx, fz_output *out)
 	return out->tell(ctx, out->state);
 }
 
+fz_stream *
+fz_stream_from_output(fz_context *ctx, fz_output *out)
+{
+	if (!out) return 0;
+	if (out->as_stream == NULL)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "Cannot derive input stream from output stream");
+	return out->as_stream(ctx, out->state);
+}
+
 static void
 fz_write_emit(fz_context *ctx, void *out, int c)
 {
diff --git a/source/fitz/stream-open.c b/source/fitz/stream-open.c
index ffd61b66..1a99ad52 100644
--- a/source/fitz/stream-open.c
+++ b/source/fitz/stream-open.c
@@ -144,6 +144,14 @@ fz_open_file_ptr(fz_context *ctx, FILE *file)
 	return stm;
 }
 
+fz_stream *fz_open_file_ptr_no_close(fz_context *ctx, FILE *file)
+{
+	fz_stream *stm = fz_open_file_ptr(ctx, file);
+	/* We don't own the file ptr. Ensure we don't close it */
+	stm->close = NULL;
+	return stm;
+}
+
 fz_stream *
 fz_open_file(fz_context *ctx, const char *name)
 {