From 960c3b6d2229dcc7cc4a4ef60838329b78880e66 Mon Sep 17 00:00:00 2001
From: Michael Drake <michael.drake@codethink.co.uk>
Date: Mon, 3 Apr 2017 10:07:23 +0100
Subject: New LZW decoder: Add client calls to create/destroy LZW contexts.

---
 src/lzw.c | 28 ++++++++++++++++++++++++++++
 src/lzw.h | 24 ++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/src/lzw.c b/src/lzw.c
index 23c815e..4f7ff8f 100644
--- a/src/lzw.c
+++ b/src/lzw.c
@@ -41,6 +41,34 @@ struct lzw_read_ctx {
 	uint32_t sb_bit_count;  /**< Bit count in sub-block */
 };
 
+/**
+ * LZW decompression context.
+ */
+struct lzw_ctx {
+	/** Input reading context */
+	struct lzw_read_ctx input;
+};
+
+
+/* Exported function, documented in lzw.h */
+lzw_result lzw_context_create(struct lzw_ctx **ctx)
+{
+	struct lzw_ctx *c = malloc(sizeof(*c));
+	if (c == NULL) {
+		return LZW_NO_MEM;
+	}
+
+	*ctx = c;
+	return LZW_OK;
+}
+
+
+/* Exported function, documented in lzw.h */
+void lzw_context_destroy(struct lzw_ctx *ctx)
+{
+	free(ctx);
+}
+
 
 /**
  * Advance the context to the next sub-block in the input data.
diff --git a/src/lzw.h b/src/lzw.h
index 0683ad0..a908414 100644
--- a/src/lzw.h
+++ b/src/lzw.h
@@ -17,12 +17,36 @@
  */
 
 
+/* Declare lzw internal context structure */
+struct lzw_ctx;
+
+
 /** LZW decoding response codes */
 typedef enum lzw_result {
 	LZW_OK,        /**< Success */
 	LZW_OK_EOD,    /**< Success; reached zero-length sub-block */
+	LZW_NO_MEM,    /**< Error: Out of memory */
 	LZW_NO_DATA,   /**< Error: Out of data */
 } lzw_result;
 
 
+/**
+ * Create an LZW decompression context.
+ *
+ * \param[out] ctx  Returns an LZW decompression context.  Caller owned,
+ *                  free with lzw_context_destroy().
+ * \return LZW_OK on success, or appropriate error code otherwise.
+ */
+lzw_result lzw_context_create(
+		struct lzw_ctx **ctx);
+
+/**
+ * Destroy an LZW decompression context.
+ *
+ * \param[in] ctx  The LZW decompression context to destroy.
+ */
+void lzw_context_destroy(
+		struct lzw_ctx *ctx);
+
+
 #endif
-- 
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