Implement tokenization in a C extension.

ext/liquid/extconf.rb

@@ -0,0 +1,3 @@
+require 'mkmf'
+$CFLAGS << ' -Wall'
+create_makefile("liquid/liquid")

ext/liquid/liquid_ext.c

@@ -0,0 +1,9 @@
+#include "liquid_ext.h"
+
+VALUE mLiquid;
+
+void Init_liquid(void)
+{
+    mLiquid = rb_define_module("Liquid");
+    init_liquid_tokenizer();
+}

ext/liquid/liquid_ext.h

@@ -0,0 +1,8 @@
+#ifndef LIQUID_EXT_H
+#define LIQUID_EXT_H
+
+#include <ruby.h>
+#include <stdbool.h>
+#include "tokenizer.h"
+
+#endif

ext/liquid/tokenizer.c

@@ -0,0 +1,114 @@
+#include "liquid_ext.h"
+
+VALUE cLiquidTokenizer;
+extern VALUE mLiquid;
+
+static void free_tokenizer(void *ptr)
+{
+    struct liquid_tokenizer *tokenizer = ptr;
+    xfree(tokenizer);
+}
+
+static VALUE rb_allocate(VALUE klass)
+{
+    VALUE obj;
+    struct liquid_tokenizer *tokenizer;
+
+    obj = Data_Make_Struct(klass, struct liquid_tokenizer, NULL, free_tokenizer, tokenizer);
+    return obj;
+}
+
+static VALUE rb_initialize(VALUE self, VALUE source)
+{
+    struct liquid_tokenizer *tokenizer;
+
+    Check_Type(source, T_STRING);
+    Data_Get_Struct(self, struct liquid_tokenizer, tokenizer);
+    tokenizer->cursor = RSTRING_PTR(source);
+    tokenizer->length = RSTRING_LEN(source);
+    return Qnil;
+}
+
+void liquid_tokenizer_next(struct liquid_tokenizer *tokenizer, struct token *token)
+{
+    if (tokenizer->length <= 0) {
+        memset(token, 0, sizeof(*token));
+        return;
+    }
+    token->type = TOKEN_STRING;
+
+    char *cursor = tokenizer->cursor;
+    char *last = tokenizer->cursor + tokenizer->length - 1;
+
+    while (cursor < last) {
+        if (*cursor++ != '{')
+            continue;
+
+        char c = *cursor++;
+        if (c != '%' && c != '{')
+            continue;
+        if (cursor - tokenizer->cursor > 2) {
+            token->type = TOKEN_STRING;
+            cursor -= 2;
+            goto found;
+        }
+        char *incomplete_end = cursor;
+        token->type = TOKEN_INVALID;
+        if (c == '%') {
+            while (cursor < last) {
+                if (*cursor++ != '%')
+                    continue;
+                c = *cursor++;
+                while (c == '%' && cursor <= last)
+                    c = *cursor++;
+                if (c != '}')
+                    continue;
+                token->type = TOKEN_TAG;
+                goto found;
+            }
+            cursor = incomplete_end;
+            goto found;
+        } else {
+            while (cursor < last) {
+                if (*cursor++ != '}')
+                    continue;
+                if (*cursor++ != '}') {
+                    incomplete_end = cursor - 1;
+                    continue;
+                }
+                token->type = TOKEN_VARIABLE;
+                goto found;
+            }
+            cursor = incomplete_end;
+            goto found;
+        }
+    }
+    cursor = last + 1;
+found:
+    token->str = tokenizer->cursor;
+    token->length = cursor - tokenizer->cursor;
+    tokenizer->cursor += token->length;
+    tokenizer->length -= token->length;
+}
+
+static VALUE rb_next(VALUE self)
+{
+    struct liquid_tokenizer *tokenizer;
+    Data_Get_Struct(self, struct liquid_tokenizer, tokenizer);
+
+    struct token token;
+    liquid_tokenizer_next(tokenizer, &token);
+    if (token.type == TOKEN_NONE)
+        return Qnil;
+
+    return rb_str_new(token.str, token.length);
+}
+
+void init_liquid_tokenizer()
+{
+    cLiquidTokenizer = rb_define_class_under(mLiquid, "Tokenizer", rb_cObject);
+    rb_define_alloc_func(cLiquidTokenizer, rb_allocate);
+    rb_define_method(cLiquidTokenizer, "initialize", rb_initialize, 1);
+    rb_define_method(cLiquidTokenizer, "next", rb_next, 0);
+    rb_define_alias(cLiquidTokenizer, "shift", "next");
+}

ext/liquid/tokenizer.h

@@ -0,0 +1,26 @@
+#ifndef LIQUID_TOKENIZER_H
+#define LIQUID_TOKENIZER_H
+
+enum token_type {
+    TOKEN_NONE,
+    TOKEN_INVALID,
+    TOKEN_STRING,
+    TOKEN_TAG,
+    TOKEN_VARIABLE
+};
+
+struct token {
+    enum token_type type;
+    char *str;
+    int length;
+};
+
+struct liquid_tokenizer {
+    char *cursor;
+    int length;
+};
+
+void init_liquid_tokenizer();
+void liquid_tokenizer_next(struct liquid_tokenizer *tokenizer, struct token *token);
+
+#endif