lzw: Add function for decoding multiple LZW codes at a time.

2 files changed, 41 insertions, 0 deletions

diff --git a/src/lzw.c b/src/lzw.c
index 8c8911a..2f604e4 100644
--- a/src/lzw.c
+++ b/src/lzw.c
@@ -426,3 +426,29 @@ lzw_result lzw_decode(struct lzw_ctx *ctx,
 	return lzw__decode(ctx, ctx->stack_base, sizeof(ctx->stack_base),
 			lzw__write_pixels, used);
 }
+
+/* Exported function, documented in lzw.h */
+lzw_result lzw_decode_continuous(struct lzw_ctx *ctx,
+		const uint8_t ** const data,
+		uint32_t *used)
+{
+	*used = 0;
+	*data = ctx->stack_base;
+
+	if (ctx->output_left != 0) {
+		*used += lzw__write_pixels(ctx,
+				ctx->stack_base, sizeof(ctx->stack_base), *used,
+				ctx->output_code, ctx->output_left);
+	}
+
+	while (*used != sizeof(ctx->stack_base)) {
+		lzw_result res = lzw__decode(ctx,
+				ctx->stack_base, sizeof(ctx->stack_base),
+				lzw__write_pixels, used);
+		if (res != LZW_OK) {
+			return res;
+		}
+	}
+
+	return LZW_OK;
+}
diff --git a/src/lzw.h b/src/lzw.h
index 4b6bfab..ec7709a 100644
--- a/src/lzw.h
+++ b/src/lzw.h
@@ -91,4 +91,19 @@ lzw_result lzw_decode(struct lzw_ctx *ctx,
 		const uint8_t ** const data,
 		uint32_t *used);
 
+/**
+ * Read input codes until end of input or output buffer is full.
+ *
+ * Ensure anything on the stack is used before calling this, as anything
+ * on the stack before this call will be trampled.
+ *
+ * \param[in]  ctx   LZW reading context, updated.
+ * \param[out] data  Returns pointer to array of output values.
+ * \param[out] used  Returns the number of values written to data.
+ * \return LZW_OK on success, or appropriate error code otherwise.
+ */
+lzw_result lzw_decode_continuous(struct lzw_ctx *ctx,
+		const uint8_t ** const data,
+		uint32_t *used);
+
 #endif