Handle serialization endianness transparently (#152)

Change JS_WriteObject() and JS_WriteObject2() to write little-endian
data and update JS_ReadObject() to byte-swap data when running on a
big-endian system.

Obsoletes the JS_WRITE_OBJ_BSWAP flag, it is now a no-op.

Fixes: #125

Author: bnoordhuis

doc/quickjs.texi

@@ -167,9 +167,6 @@ find the name of the dynamically loaded modules.
 Add initialization code for an external C module. See the
 @code{c_module} example.
 
-@item -x
-Byte swapped output (only used for cross compilation).
-
 @item -flto
 Use link time optimization. The compilation is slower but the
 executable is smaller and faster. This option is automatically set

qjsc.c

@@ -51,7 +51,6 @@ static namelist_t cname_list;
 static namelist_t cmodule_list;
 static namelist_t init_module_list;
 static FILE *outfile;
-static BOOL byte_swap;
 static const char *c_ident_prefix = "qjsc_";
 
 
@@ -152,11 +151,8 @@ static void output_object_code(JSContext *ctx,
 {
     uint8_t *out_buf;
     size_t out_buf_len;
-    int flags;
-    flags = JS_WRITE_OBJ_BYTECODE;
-    if (byte_swap)
-        flags |= JS_WRITE_OBJ_BSWAP;
-    out_buf = JS_WriteObject(ctx, &out_buf_len, obj, flags);
+
+    out_buf = JS_WriteObject(ctx, &out_buf_len, obj, JS_WRITE_OBJ_BYTECODE);
     if (!out_buf) {
         js_std_dump_error(ctx);
         exit(1);
@@ -322,7 +318,6 @@ void help(void)
            "-m          compile as Javascript module (default=autodetect)\n"
            "-D module_name         compile a dynamically loaded module or worker\n"
            "-M module_name[,cname] add initialization code for an external C module\n"
-           "-x          byte swapped output\n"
            "-p prefix   set the prefix of the generated C names\n"
            "-S n        set the maximum stack size to 'n' bytes (default=%d)\n",
            JS_GetVersion(),
@@ -352,7 +347,6 @@ int main(int argc, char **argv)
     output_type = OUTPUT_C;
     cname = NULL;
     module = -1;
-    byte_swap = FALSE;
     verbose = 0;
     stack_size = 0;
     memset(&dynamic_module_list, 0, sizeof(dynamic_module_list));
@@ -399,9 +393,6 @@ int main(int argc, char **argv)
         case 'D':
             namelist_add(&dynamic_module_list, optarg, NULL, 0);
             break;
-        case 'x':
-            byte_swap = TRUE;
-            break;
         case 'v':
             verbose++;
             break;

quickjs.c

@@ -31664,18 +31664,11 @@ typedef enum BCTagEnum {
     BC_TAG_OBJECT_REFERENCE,
 } BCTagEnum;
 
-#define BC_BASE_VERSION 2
-#define BC_BE_VERSION 0x40
-#ifdef WORDS_BIGENDIAN
-#define BC_VERSION (BC_BASE_VERSION | BC_BE_VERSION)
-#else
-#define BC_VERSION BC_BASE_VERSION
-#endif
+#define BC_VERSION 3
 
 typedef struct BCWriterState {
     JSContext *ctx;
     DynBuf dbuf;
-    BOOL byte_swap : 8;
     BOOL allow_bytecode : 8;
     BOOL allow_sab : 8;
     BOOL allow_reference : 8;
@@ -31717,28 +31710,37 @@ static const char * const bc_tag_str[] = {
 };
 #endif
 
+static inline BOOL is_be(void)
+{
+    union {
+        uint16_t a;
+        uint8_t  b;
+    } u = {0x100};
+    return u.b;
+}
+
 static void bc_put_u8(BCWriterState *s, uint8_t v)
 {
     dbuf_putc(&s->dbuf, v);
 }
 
 static void bc_put_u16(BCWriterState *s, uint16_t v)
 {
-    if (s->byte_swap)
+    if (is_be())
         v = bswap16(v);
     dbuf_put_u16(&s->dbuf, v);
 }
 
 static __maybe_unused void bc_put_u32(BCWriterState *s, uint32_t v)
 {
-    if (s->byte_swap)
+    if (is_be())
         v = bswap32(v);
     dbuf_put_u32(&s->dbuf, v);
 }
 
 static void bc_put_u64(BCWriterState *s, uint64_t v)
 {
-    if (s->byte_swap)
+    if (is_be())
         v = bswap64(v);
     dbuf_put(&s->dbuf, (uint8_t *)&v, sizeof(v));
 }
@@ -31908,7 +31910,7 @@ static int JS_WriteFunctionBytecode(BCWriterState *s,
         pos += len;
     }
 
-    if (s->byte_swap)
+    if (is_be())
         bc_byte_swap(bc_buf, bc_len);
 
     dbuf_put(&s->dbuf, bc_buf, bc_len);
@@ -32405,15 +32407,10 @@ static int JS_WriteObjectAtoms(BCWriterState *s)
     JSRuntime *rt = s->ctx->rt;
     DynBuf dbuf1;
     int i, atoms_size;
-    uint8_t version;
 
     dbuf1 = s->dbuf;
     js_dbuf_init(s->ctx, &s->dbuf);
-
-    version = BC_VERSION;
-    if (s->byte_swap)
-        version ^= BC_BE_VERSION;
-    bc_put_u8(s, version);
+    bc_put_u8(s, BC_VERSION);
 
     bc_put_leb128(s, s->idx_to_atom_count);
     for(i = 0; i < s->idx_to_atom_count; i++) {
@@ -32446,8 +32443,6 @@ uint8_t *JS_WriteObject2(JSContext *ctx, size_t *psize, JSValueConst obj,
 
     memset(s, 0, sizeof(*s));
     s->ctx = ctx;
-    /* XXX: byte swapped output is untested */
-    s->byte_swap = ((flags & JS_WRITE_OBJ_BSWAP) != 0);
     s->allow_bytecode = ((flags & JS_WRITE_OBJ_BYTECODE) != 0);
     s->allow_sab = ((flags & JS_WRITE_OBJ_SAB) != 0);
     s->allow_reference = ((flags & JS_WRITE_OBJ_REFERENCE) != 0);
@@ -33531,7 +33526,6 @@ static int JS_ReadObjectAtoms(BCReaderState *s)
 
     if (bc_get_u8(s, &v8))
         return -1;
-    /* XXX: could support byte swapped input */
     if (v8 != BC_VERSION) {
         JS_ThrowSyntaxError(s->ctx, "invalid version (%d expected=%d)",
                             v8, BC_VERSION);

quickjs.h

@@ -838,7 +838,7 @@ JS_EXTERN int JS_ExecutePendingJob(JSRuntime *rt, JSContext **pctx);
 
 /* Object Writer/Reader (currently only used to handle precompiled code) */
 #define JS_WRITE_OBJ_BYTECODE  (1 << 0) /* allow function/module */
-#define JS_WRITE_OBJ_BSWAP     (1 << 1) /* byte swapped output */
+#define JS_WRITE_OBJ_BSWAP     (0)      /* byte swapped output (obsolete, handled transparently) */
 #define JS_WRITE_OBJ_SAB       (1 << 2) /* allow SharedArrayBuffer */
 #define JS_WRITE_OBJ_REFERENCE (1 << 3) /* allow object references to
                                            encode arbitrary object