Implement tokenization in a C extension.

ext/liquid/extconf.rb

@@ -0,0 +1,4 @@
+require 'mkmf'
+$CFLAGS << ' -Wall -Werror'
+$warnflags.gsub!(/-Wdeclaration-after-statement/, "")
+create_makefile("liquid/liquid")

ext/liquid/liquid.c

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

ext/liquid/liquid.h

@@ -0,0 +1,11 @@
+#ifndef LIQUID_H
+#define LIQUID_H
+
+#include <ruby.h>
+#include <stdbool.h>
+
+#include "tokenizer.h"
+
+extern VALUE mLiquid;
+
+#endif

ext/liquid/tokenizer.c

@@ -0,0 +1,137 @@
+#include "liquid.h"
+
+VALUE cLiquidTokenizer;
+
+static void tokenizer_mark(void *ptr) {
+    tokenizer_t *tokenizer = ptr;
+    rb_gc_mark(tokenizer->source);
+}
+
+static void tokenizer_free(void *ptr)
+{
+    tokenizer_t *tokenizer = ptr;
+    xfree(tokenizer);
+}
+
+static size_t tokenizer_memsize(const void *ptr)
+{
+    return ptr ? sizeof(tokenizer_t) : 0;
+}
+
+const rb_data_type_t tokenizer_data_type = {
+    "liquid_tokenizer",
+    {tokenizer_mark, tokenizer_free, tokenizer_memsize,},
+#ifdef RUBY_TYPED_FREE_IMMEDIATELY
+    NULL, NULL, RUBY_TYPED_FREE_IMMEDIATELY
+#endif
+};
+
+static VALUE tokenizer_allocate(VALUE klass)
+{
+    VALUE obj;
+    tokenizer_t *tokenizer;
+
+    obj = TypedData_Make_Struct(klass, tokenizer_t, &tokenizer_data_type, tokenizer);
+    tokenizer->source = Qnil;
+    return obj;
+}
+
+static VALUE tokenizer_initialize_method(VALUE self, VALUE source)
+{
+    tokenizer_t *tokenizer;
+
+    Check_Type(source, T_STRING);
+    Tokenizer_Get_Struct(self, tokenizer);
+    source = rb_str_dup_frozen(source);
+    tokenizer->source = source;
+    tokenizer->cursor = RSTRING_PTR(source);
+    tokenizer->length = RSTRING_LEN(source);
+    return Qnil;
+}
+
+void tokenizer_next(tokenizer_t *tokenizer, token_t *token)
+{
+    if (tokenizer->length <= 0) {
+        memset(token, 0, sizeof(*token));
+        return;
+    }
+
+    const char *cursor = tokenizer->cursor;
+    const char *last = cursor + tokenizer->length - 1;
+
+    token->str = cursor;
+    token->type = TOKEN_STRING;
+
+    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;
+        }
+        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;
+            }
+            // unterminated tag
+            cursor = tokenizer->cursor + 2;
+            goto found;
+        } else {
+            while (cursor < last) {
+                if (*cursor++ != '}')
+                    continue;
+                if (*cursor++ != '}') {
+                    // variable incomplete end, used to end raw tags
+                    cursor--;
+                    goto found;
+                }
+                token->type = TOKEN_VARIABLE;
+                goto found;
+            }
+            // unterminated variable
+            cursor = tokenizer->cursor + 2;
+            goto found;
+        }
+    }
+    cursor = last + 1;
+found:
+    token->length = cursor - tokenizer->cursor;
+    tokenizer->cursor += token->length;
+    tokenizer->length -= token->length;
+}
+
+static VALUE tokenizer_next_method(VALUE self)
+{
+    tokenizer_t *tokenizer;
+    Tokenizer_Get_Struct(self, tokenizer);
+
+    token_t token;
+    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, tokenizer_allocate);
+    rb_define_method(cLiquidTokenizer, "initialize", tokenizer_initialize_method, 1);
+    rb_define_method(cLiquidTokenizer, "next", tokenizer_next_method, 0);
+    rb_define_alias(cLiquidTokenizer, "shift", "next");
+}

ext/liquid/tokenizer.h

@@ -0,0 +1,31 @@
+#ifndef LIQUID_TOKENIZER_H
+#define LIQUID_TOKENIZER_H
+
+enum token_type {
+    TOKEN_NONE,
+    TOKEN_INVALID,
+    TOKEN_STRING,
+    TOKEN_TAG,
+    TOKEN_VARIABLE
+};
+
+typedef struct token {
+    enum token_type type;
+    const char *str;
+    long length;
+} token_t;
+
+typedef struct tokenizer {
+    VALUE source;
+    const char *cursor;
+    long length;
+} tokenizer_t;
+
+extern VALUE cLiquidTokenizer;
+extern const rb_data_type_t tokenizer_data_type;
+#define Tokenizer_Get_Struct(obj, sval) TypedData_Get_Struct(obj, tokenizer_t, &tokenizer_data_type, sval)
+
+void init_liquid_tokenizer();
+void tokenizer_next(tokenizer_t *tokenizer, token_t *token);
+
+#endif