Refactor compressed stream loading.

Refactor 'short stopped' image stream loading into fz_compressed_buffer
loading. Nicer overall, and reflects the fact that this can be used
for non-image streams that we want to hold compressed in memory (for
instance for shading streams).

This is a preparatory step for pdfwrite, and enables further shading
memory use optimisations.

Remove unused jbig2 function pointer from the fz_compression_params
(previously fz_image_params) structure to avoid confusion.

2 files changed, 134 insertions, 0 deletions

diff --git a/fitz/fitz-internal.h b/fitz/fitz-internal.h
index b923429f..5c9270a1 100644
--- a/fitz/fitz-internal.h
+++ b/fitz/fitz-internal.h
@@ -694,6 +694,72 @@ fz_pixmap *fz_scale_pixmap(fz_context *ctx, fz_pixmap *src, float x, float y, fl
 
 fz_bbox fz_pixmap_bbox_no_ctx(fz_pixmap *src);
 
+typedef struct fz_compression_params_s fz_compression_params;
+
+typedef struct fz_compressed_buffer_s fz_compressed_buffer;
+
+fz_stream *fz_open_image_decomp_stream(fz_context *ctx, fz_compressed_buffer *, int *factor);
+
+enum
+{
+	FZ_IMAGE_UNKNOWN = 0,
+	FZ_IMAGE_JPEG = 1,
+	FZ_IMAGE_JPX = 2, /* Placeholder until supported */
+	FZ_IMAGE_FAX = 3,
+	FZ_IMAGE_JBIG2 = 4, /* Placeholder until supported */
+	FZ_IMAGE_RAW = 5,
+	FZ_IMAGE_RLD = 6,
+	FZ_IMAGE_FLATE = 7,
+	FZ_IMAGE_LZW = 8
+};
+
+struct fz_compression_params_s
+{
+	int type;
+	union {
+		struct {
+			int color_transform;
+		} jpeg;
+		struct {
+			int smask_in_data;
+		} jpx;
+		struct {
+			int columns;
+			int rows;
+			int k;
+			int end_of_line;
+			int encoded_byte_align;
+			int end_of_block;
+			int black_is_1;
+			int damaged_rows_before_error;
+		} fax;
+		struct
+		{
+			int columns;
+			int colors;
+			int predictor;
+			int bpc;
+		}
+		flate;
+		struct
+		{
+			int columns;
+			int colors;
+			int predictor;
+			int bpc;
+			int early_change;
+		} lzw;
+	} u;
+};
+
+struct fz_compressed_buffer_s
+{
+	fz_compression_params params;
+	fz_buffer *buffer;
+};
+
+void fz_free_compressed_buffer(fz_context *ctx, fz_compressed_buffer *buf);
+
 struct fz_image_s
 {
 	fz_storable storable;
diff --git a/fitz/stm_comp_buf.c b/fitz/stm_comp_buf.c
new file mode 100644
index 00000000..93df0ef0
--- /dev/null
+++ b/fitz/stm_comp_buf.c
@@ -0,0 +1,68 @@
+#include "fitz-internal.h"
+
+/* This code needs to be kept out of stm_buffer.c to avoid it being
+ * pulled into cmapdump.c */
+
+void
+fz_free_compressed_buffer(fz_context *ctx, fz_compressed_buffer *buf)
+{
+	if (!buf)
+		return;
+
+	fz_drop_buffer(ctx, buf->buffer);
+	fz_free(ctx, buf);
+}
+
+
+fz_stream *
+fz_open_image_decomp_stream(fz_context *ctx, fz_compressed_buffer *buffer, int *factor)
+{
+	fz_stream *chain = fz_open_buffer(ctx, buffer->buffer);
+	fz_compression_params *params = &buffer->params;
+
+	switch (params->type)
+	{
+	case FZ_IMAGE_FAX:
+		*factor = 1;
+		return fz_open_faxd(chain,
+				params->u.fax.k,
+				params->u.fax.end_of_line,
+				params->u.fax.encoded_byte_align,
+				params->u.fax.columns,
+				params->u.fax.rows,
+				params->u.fax.end_of_block,
+				params->u.fax.black_is_1);
+	case FZ_IMAGE_JPEG:
+		if (*factor > 8)
+			*factor = 8;
+		return fz_open_resized_dctd(chain, params->u.jpeg.color_transform, *factor);
+	case FZ_IMAGE_RLD:
+		*factor = 1;
+		return fz_open_rld(chain);
+	case FZ_IMAGE_FLATE:
+		*factor = 1;
+		chain = fz_open_flated(chain);
+		if (params->u.flate.predictor > 1)
+			chain = fz_open_predict(chain, params->u.flate.predictor, params->u.flate.columns, params->u.flate.colors, params->u.flate.bpc);
+		return chain;
+	case FZ_IMAGE_LZW:
+		*factor = 1;
+		chain = fz_open_lzwd(chain, params->u.lzw.early_change);
+		if (params->u.lzw.predictor > 1)
+			chain = fz_open_predict(chain, params->u.lzw.predictor, params->u.lzw.columns, params->u.lzw.colors, params->u.lzw.bpc);
+		return chain;
+	default:
+		*factor = 1;
+		break;
+	}
+
+	return chain;
+}
+
+fz_stream *
+fz_open_compressed_stream(fz_context *ctx, fz_compressed_buffer *buffer)
+{
+	int factor = 1;
+
+	return fz_open_image_decomp_stream(ctx, buffer, &factor);
+}