Add support for lua.gsub()

Author: thsackos

README.md

@@ -86,7 +86,7 @@ you.
 | API                         | Support                               |
 |-----------------------------|---------------------------------------|
 | Lua C API (`lua_*`)         | 🎉 100% coverage<sup>†</sup> (92/92)  |
-| Auxilary Library (`luaL_*`) | 52% coverage (26/48)                  |
+| Auxilary Library (`luaL_*`) | 54% coverage (27/48)                  |
 | LuaJIT Extensions           | *No plans to implement.*              |
 
 *†: Coroutine yield/resume is not yet part of the public `zig-luajit` Zig API, see [#6][ISSUE-6].*
@@ -248,7 +248,7 @@ The `zig-luajit` project has not yet reached the 1.0 release, the API is subject
 | `luaL_error`               | ☑️📢 `lua.raiseErrorFormat()` |
 | `luaL_getmetafield`        ||
 | `luaL_getmetatable`        ||
-| `luaL_gsub`                ||
+| `luaL_gsub`                | ☑️ `lua.gsub()` |
 | `luaL_loadbuffer`          ||
 | `luaL_loadfile`            ||
 | `luaL_loadstring`          ||

src/lual_api.zig

@@ -106,14 +106,6 @@ pub fn getMetaField(lua: *Lua, obj: i32, e: [:0]const u8) i32;
 /// Stack Behavior: `[-0, +1, -]`
 pub fn getMetatable(lua: *Lua, name: [*:0]const u8) void;
 
-/// Creates a copy of string s by replacing any occurrence of the string p with the string r.
-/// Pushes the resulting string on the stack and returns it.
-///
-/// From: `const char *luaL_gsub(lua_State *L, const char *s, const char *p, const char *r);`
-/// Refer to: https://www.lua.org/manual/5.1/manual.html#luaL_gsub
-/// Stack Behavior: `[-0, +1, m]`
-pub fn gSub(lua: *Lua, s: []const u8, p: []const u8, r: []const u8) []const u8;
-
 /// Loads a buffer as a Lua chunk using lua_load to load the chunk in the buffer pointed to by buff with size sz.
 /// Returns the same results as lua_load. The name parameter is used for debug information and error messages.
 ///

src/root.zig

@@ -2253,6 +2253,34 @@ pub const Lua = opaque {
             @ptrCast(functions.ptr),
         );
     }
+
+    /// Performs a `[g]lobal [sub]stitution` of content in the given `string` replacing all occurrences of the substring
+    /// `pattern` with the content `replacement`.
+    ///
+    /// Pushes the resulting string on the stack and returns it.
+    ///
+    /// From: `const char *luaL_gsub(lua_State *L, const char *s, const char *p, const char *r);`
+    /// Refer to: https://www.lua.org/manual/5.1/manual.html#luaL_gsub
+    /// Stack Behavior: `[-0, +1, m]`
+    pub fn gsub(lua: *Lua, string: [:0]const u8, pattern: [:0]const u8, replacement: [:0]const u8) [:0]const u8 {
+        assert(pattern.len > 0); // gsub(string, "", replacement) causes an infinite loop -- avoid using the empty string as a pattern.
+
+        const str: ?[*:0]const u8 = c.luaL_gsub(asState(lua), @ptrCast(string.ptr), @ptrCast(pattern.ptr), @ptrCast(replacement.ptr));
+        if (str) |s| {
+            const len = std.mem.indexOfSentinel(u8, 0, s);
+            return s[0..len :0];
+        } else {
+            lua.raiseErrorFormat(
+                "gsub('%s', '%s', '%s') returned null instead of the replaced string.",
+                .{
+                    string.ptr,
+                    pattern.ptr,
+                    replacement.ptr,
+                },
+            );
+            unreachable;
+        }
+    }
 };
 
 test "Lua can be initialized with an allocator" {
@@ -4225,3 +4253,19 @@ test "suspend and resume coroutines" {
     // TODO: This does not return the expected behavior - I do not think yield and resume work as expected.
     // try std.testing.expectEqual(20, try thread.toIntegerStrict(-1));
 }
+
+test "gsub" {
+    const lua = try Lua.init(std.testing.allocator);
+    defer lua.deinit();
+
+    const string = "ABBA";
+    const pattern = "B";
+    const replacement = "C";
+    const expected = "ACCA";
+
+    const actual = lua.gsub(string, pattern, replacement);
+
+    try std.testing.expectEqual(1, lua.getTop());
+    try std.testing.expectEqualStrings(expected, try lua.toLString(-1));
+    try std.testing.expectEqualStrings(expected, actual);
+}