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fix(parser): prevent chunk from being garbage collected #3

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fix(parser): prevent chunk from being garbage collected #3

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21 changes: 12 additions & 9 deletions src/parser.c
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Original file line number Diff line number Diff line change
Expand Up @@ -103,24 +103,28 @@ static const char *read(
InputContext *ctx = payload;
lua_State *L = ctx->L;

// We delay popping the results of the reader function until the next
// read cycle in order to prevent the requested chunk from being garbage
// collected in a multithreaded Lua environment.
lua_pop(L, 2);
lua_pushvalue(L, -1);
lua_pushinteger(L, byte_index);
LTS_push_point(L, position);
if (lua_pcall(L, 2, 2, 0) != 0) {
ctx->status = LTS_INPUT_RTERROR;
goto fail_no_pop;
goto fail;
}

switch (lua_type(L, -2)) {
case LUA_TNIL:
goto fail_pop;
goto fail;

case LUA_TSTRING:
break;

default:
ctx->status = LTS_INPUT_RETTYPE_1;
goto fail_pop;
goto fail;
}

size_t offset;
Expand All @@ -135,23 +139,20 @@ static const char *read(

default:
ctx->status = LTS_INPUT_RETTYPE_2;
goto fail_pop;
goto fail;
}

size_t len;
const char *str = lua_tolstring(L, -2, &len);
lua_pop(L, 2);

if (offset > len) goto fail_no_pop;
if (offset > len) goto fail;
if (offset < 1) offset += len + 1;
if (offset < 1) offset = 1;

*bytes_read = len - offset + 1;
return str + offset - 1;

fail_pop:
lua_pop(L, 2);
fail_no_pop:
fail:
*bytes_read = 0;
return NULL;
}
Expand All @@ -172,6 +173,8 @@ static int LTS_parser_parse(lua_State *L) {
.encoding = TSInputEncodingUTF8,
};

lua_pushnil(L);
lua_pushnil(L);
TSTree *tree = ts_parser_parse(self, old_tree, input);

switch (ctx.status) {
Expand Down