backport Lua 5.2/5.3 buffer API for Lua 5.1

5 files changed, 127 insertions, 7 deletions

diff --git a/README.md b/README.md
index c04d2d1..359cc3f 100644
--- a/README.md
+++ b/README.md
@@ -129,6 +129,7 @@ For Lua 5.1 additionally:
 * `luaL_fileresult`
 * `luaL_checkversion` (with empty body, only to avoid compile errors)
 * `luaL_tolstring`
+* `luaL_buffinitsize`, `luaL_prepbuffsize`, and `luaL_pushresultsize`
 * `lua_pushunsigned`, `lua_tounsignedx`, `lua_tounsigned`,
   `luaL_checkunsigned`, `luaL_optunsigned`, if
   `LUA_COMPAT_APIINTCASTS` is defined.
@@ -149,12 +150,9 @@ For Lua 5.1 additionally:
   * `lua_upvaluejoin` (5.1)
   * `lua_version` (5.1)
   * `lua_yieldk` (5.1)
-  * `luaL_buffinitsize` (5.1)
   * `luaL_execresult` (5.1)
   * `luaL_loadbufferx` (5.1)
   * `luaL_loadfilex` (5.1)
-  * `luaL_prepbuffsize` (5.1)
-  * `luaL_pushresultsize` (5.1)
 
 ## See also
 
diff --git a/c-api/compat-5.3.c b/c-api/compat-5.3.c
index a539aed..8db5189 100644
--- a/c-api/compat-5.3.c
+++ b/c-api/compat-5.3.c
@@ -391,6 +391,63 @@ COMPAT53_API int luaL_fileresult (lua_State *L, int stat, const char *fname) {
 #endif /* not COMPAT53_IS_LUAJIT */
 
 
+COMPAT53_API void luaL_buffinit (lua_State *L, luaL_Buffer_53 *B) {
+  /* make it crash if used via pointer to a 5.1-style luaL_Buffer */
+  B->b.p = NULL;
+  B->b.L = NULL;
+  B->b.lvl = 0;
+  /* reuse the buffer from the 5.1-style luaL_Buffer though! */
+  B->ptr = B->b.buffer;
+  B->capacity = LUAL_BUFFERSIZE;
+  B->nelems = 0;
+  B->L2 = L;
+}
+
+
+COMPAT53_API char *luaL_prepbuffsize (luaL_Buffer_53 *B, size_t s) {
+  if (B->capacity - B->nelems < s) { /* needs to grow */
+    char* newptr = NULL;
+    size_t newcap = B->capacity * 2;
+    if (newcap - B->nelems < s)
+      newcap = B->nelems + s;
+    if (newcap < B->capacity) /* overflow */
+      luaL_error(B->L2, "buffer too large");
+    newptr = lua_newuserdata(B->L2, newcap);
+    memcpy(newptr, B->ptr, B->nelems);
+    if (B->ptr != B->b.buffer)
+      lua_replace(B->L2, -2); /* remove old buffer */
+    B->ptr = newptr;
+    B->capacity = newcap;
+  }
+  return B->ptr+B->nelems;
+}
+
+
+COMPAT53_API void luaL_addlstring (luaL_Buffer_53 *B, const char *s, size_t l) {
+  memcpy(luaL_prepbuffsize(B, l), s, l);
+  luaL_addsize(B, l);
+}
+
+
+COMPAT53_API void luaL_addvalue (luaL_Buffer_53 *B) {
+  size_t len = 0;
+  const char *s = lua_tolstring(B->L2, -1, &len);
+  if (!s)
+    luaL_error(B->L2, "cannot convert value to string");
+  if (B->ptr != B->b.buffer)
+    lua_insert(B->L2, -2); /* userdata buffer must be at stack top */
+  luaL_addlstring(B, s, len);
+  lua_remove(B->L2, B->ptr != B->b.buffer ? -2 : -1);
+}
+
+
+void luaL_pushresult (luaL_Buffer_53 *B) {
+  lua_pushlstring(B->L2, B->ptr, B->nelems);
+  if (B->ptr != B->b.buffer)
+    lua_replace(B->L2, -2); /* remove userdata buffer */
+}
+
+
 #endif /* Lua 5.1 */
 
 
diff --git a/c-api/compat-5.3.h b/c-api/compat-5.3.h
index 8f38719..51bf7eb 100644
--- a/c-api/compat-5.3.h
+++ b/c-api/compat-5.3.h
@@ -3,6 +3,7 @@
 
 #include <stddef.h>
 #include <limits.h>
+#include <string.h>
 #include <lua.h>
 #include <lauxlib.h>
 #include <lualib.h>
@@ -45,12 +46,9 @@
  * lua_upvaluejoin
  * lua_version
  * lua_yieldk
- * luaL_buffinitsize
  * luaL_execresult
  * luaL_loadbufferx
  * luaL_loadfilex
- * luaL_prepbuffsize
- * luaL_pushresultsize
  */
 
 /* PUC-Rio Lua uses lconfig_h as include guard for luaconf.h,
@@ -80,6 +78,15 @@ typedef struct luaL_Stream {
 
 typedef size_t lua_Unsigned;
 
+typedef struct luaL_Buffer_53 {
+  luaL_Buffer b; /* make incorrect code crash! */
+  char *ptr;
+  size_t nelems;
+  size_t capacity;
+  lua_State *L2;
+} luaL_Buffer_53;
+#define luaL_Buffer luaL_Buffer_53
+
 #define lua_absindex COMPAT53_CONCAT(COMPAT53_PREFIX, _absindex)
 COMPAT53_API int lua_absindex (lua_State *L, int i);
 
@@ -156,6 +163,46 @@ COMPAT53_API int luaL_fileresult (lua_State *L, int stat, const char *fname);
 #define lua_pcallk(L, na, nr, err, ctx, cont) \
   ((void)(ctx), (void)(cont), lua_pcall(L, na, nr, err))
 
+#define luaL_buffinit COMPAT53_CONCAT(COMPAT53_PREFIX, _buffinit_53)
+COMPAT53_API void luaL_buffinit (lua_State *L, luaL_Buffer_53 *B);
+
+#define luaL_prepbuffsize COMPAT53_CONCAT(COMPAT53_PREFIX, _prepbufsize_53)
+COMPAT53_API char *luaL_prepbuffsize (luaL_Buffer_53 *B, size_t s);
+
+#define luaL_addlstring COMPAT53_CONCAT(COMPAT53_PREFIX, _addlstring_53)
+COMPAT53_API void luaL_addlstring (luaL_Buffer_53 *B, const char *s, size_t l);
+
+#define luaL_addvalue COMPAT53_CONCAT(COMPAT53_PREFIX, _addvalue_53)
+COMPAT53_API void luaL_addvalue (luaL_Buffer_53 *B);
+
+#define luaL_pushresult COMPAT53_CONCAT(COMPAT53_PREFIX, _pushresult_53)
+COMPAT53_API void luaL_pushresult (luaL_Buffer_53 *B);
+
+#undef luaL_buffinitsize
+#define luaL_buffinitsize(L, B, s) \
+  (luaL_buffinit(L, B), luaL_prepbuffsize(B, s))
+
+#undef luaL_prepbuffer
+#define luaL_prepbuffer(B) \
+  luaL_prepbuffsize(B, LUAL_BUFFERSIZE)
+
+#undef luaL_addchar
+#define luaL_addchar(B, c) \
+  ((void)((B)->nelems < (B)->capacity || luaL_prepbuffsize(B, 1)), \
+   ((B)->ptr[(B)->nelems++] = (c)))
+
+#undef luaL_addsize
+#define luaL_addsize(B, s) \
+  ((B)->nelems += (s))
+
+#undef luaL_addstring
+#define luaL_addstring(B, s) \
+  luaL_addlstring(B, s, strlen(s))
+
+#undef luaL_pushresultsize
+#define luaL_pushresultsize(B, s) \
+  (luaL_addsize(B, s), luaL_pushresult(B))
+
 #if defined(LUA_COMPAT_APIINTCASTS)
 #define lua_pushunsigned(L, n) \
   lua_pushinteger(L, (lua_Integer)(n))
@@ -216,7 +263,7 @@ COMPAT53_API size_t lua_stringtonumber (lua_State *L, const char *s);
 #define luaL_getmetafield(L, o, e) \
   (luaL_getmetafield(L, o, e) ? lua_type(L, -1) : LUA_TNIL)
 
-#define luaL_requiref COMPAT53_CONCAT(COMPAT53_PREFIX, L_requiref_)
+#define luaL_requiref COMPAT53_CONCAT(COMPAT53_PREFIX, L_requiref_53)
 COMPAT53_API void luaL_requiref (lua_State *L, const char *modname,
                                  lua_CFunction openf, int glb );
 
diff --git a/tests/test.lua b/tests/test.lua
index 98259fe..83e174e 100755
--- a/tests/test.lua
+++ b/tests/test.lua
@@ -679,5 +679,8 @@ local t = setmetatable({}, {
   __tostring = function(v) return nil end
 })
 print(pcall(mod.tolstring, t))
+
+___''
+print(mod.buffer())
 ___''
 
diff --git a/tests/testmod.c b/tests/testmod.c
index 2c6242b..f89b10a 100644
--- a/tests/testmod.c
+++ b/tests/testmod.c
@@ -242,6 +242,20 @@ static int test_tolstring (lua_State *L) {
   return 2;
 }
 
+static int test_buffer (lua_State *L) {
+  luaL_Buffer b;
+  char *p = luaL_buffinitsize(L, &b, LUAL_BUFFERSIZE+1);
+  p[0] = 'a';
+  p[1] = 'b';
+  luaL_addsize(&b, 2);
+  luaL_addstring(&b, "c");
+  lua_pushliteral(L, "d");
+  luaL_addvalue(&b);
+  luaL_addchar(&b, 'e');
+  luaL_pushresult(&b);
+  return 1;
+}
+
 
 static const luaL_Reg funcs[] = {
   { "isinteger", test_isinteger },
@@ -262,6 +276,7 @@ static const luaL_Reg funcs[] = {
   { "uservalue", test_uservalue },
   { "globals", test_globals },
   { "tolstring", test_tolstring },
+  { "buffer", test_buffer },
   { NULL, NULL }
 };