Support multiple primary functions in a single snapshot. (#1797)

This patch adds an extension to snapshots which allows storing
multiple position independent primary functions in a single
snapshot data. A new application called jerry-snapshot is
added to the project to manage snapshots. Currently the only
option is merging snapshots.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

jerry-core/api/jerry-snapshot.h

@@ -24,18 +24,39 @@
 typedef struct
 {
   /* The size of this structure is recommended to be divisible by
-   * JMEM_ALIGNMENT. Otherwise some bytes after the header are wasted. */
+   * uint32_t alignment. Otherwise some bytes after the header are wasted. */
+  uint32_t magic; /**< four byte magic number */
   uint32_t version; /**< version number */
-  uint32_t lit_table_offset; /**< offset of the literal table */
-  uint32_t lit_table_size; /**< size of literal table */
-  uint32_t is_run_global; /**< flag, indicating whether the snapshot
-                            *   was saved as 'Global scope'-mode code (true)
-                            *   or as eval-mode code (false) */
+  uint32_t global_flags; /**< global configuration and feature flags */
+  uint32_t lit_table_offset; /**< byte offset of the literal table */
+  uint32_t number_of_funcs; /**< number of primary ECMAScript functions */
+  uint32_t func_offsets[1]; /**< function offsets (lowest bit: global(0) or eval(1) context) */
 } jerry_snapshot_header_t;
 
 /**
- * Jerry snapshot format version
+ * Evaluate this function on the top of the scope chain.
  */
-#define JERRY_SNAPSHOT_VERSION (7u)
+#define JERRY_SNAPSHOT_EVAL_CONTEXT 0x1u
+
+/**
+ * Jerry snapshot magic marker.
+ */
+#define JERRY_SNAPSHOT_MAGIC (0x5952524Au)
+
+/**
+ * Jerry snapshot format version.
+ */
+#define JERRY_SNAPSHOT_VERSION (8u)
+
+/**
+ * Snapshot configuration flags.
+ */
+typedef enum
+{
+  /* 8 bits are reserved for dynamic features */
+  JERRY_SNAPSHOT_HAS_REGEX_LITERAL = (1u << 0), /**< byte code has regex literal */
+  /* 24 bits are reserved for compile time features */
+  JERRY_SNAPSHOT_FOUR_BYTE_CPOINTER = (1u << 8) /**< compressed pointers are four byte long */
+} jerry_snapshot_global_flags_t;
 
 #endif /* !JERRY_SNAPSHOT_H */