StringScanner#scan_integer support base 16 integers (#116)

Followup: https://github.com/ruby/strscan/pull/115

`scan_integer` is now implemented in Ruby as to efficiently handle
keyword arguments without allocating a Hash. Given the goal of
`scan_integer` is to more effciently parse integers without having to
allocate an intermediary object, using `rb_scan_args` would defeat the
purpose.

Additionally, the C implementation now uses `rb_isdigit` and
`rb_isxdigit`, because on Windows `isdigit` is locale dependent.

ext/strscan/lib/strscan/strscan.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class StringScanner
+  # call-seq:
+  #   scan_integer(base: 10)
+  # 
+  # If `base` isn't provided or is `10`, then it is equivalent to calling `#scan` with a `[+-]?\d+` pattern,
+  # and returns an Integer or nil.
+  #
+  # If `base` is `16`, then it is equivalent to calling `#scan` with a `[+-]?(0x)?[0-9a-fA-F]+` pattern,
+  # and returns an Integer or nil.
+  # 
+  # The scanned string must be encoded with an ASCII compatible encoding, otherwise
+  # Encoding::CompatibilityError will be raised.
+  def scan_integer(base: 10)
+    case base
+    when 10
+      scan_base10_integer
+    when 16
+      scan_base16_integer
+    else
+      raise ArgumentError, "Unsupported integer base: #{base.inspect}, expected 10 or 16"
+    end
+  end
+end

ext/strscan/strscan.c

@@ -20,7 +20,6 @@
 extern size_t onig_region_memsize(const struct re_registers *regs);
 #endif
 
-#include <ctype.h>
 #include <stdbool.h>
 
 #define STRSCAN_VERSION "3.1.1.dev"
@@ -116,7 +115,7 @@ static VALUE strscan_get_byte _((VALUE self));
 static VALUE strscan_getbyte _((VALUE self));
 static VALUE strscan_peek _((VALUE self, VALUE len));
 static VALUE strscan_peep _((VALUE self, VALUE len));
-static VALUE strscan_scan_integer _((VALUE self));
+static VALUE strscan_scan_base10_integer _((VALUE self));
 static VALUE strscan_unscan _((VALUE self));
 static VALUE strscan_bol_p _((VALUE self));
 static VALUE strscan_eos_p _((VALUE self));
@@ -1268,21 +1267,26 @@ strscan_peep(VALUE self, VALUE vlen)
     return strscan_peek(self, vlen);
 }
 
-/*
- * call-seq:
- *   scan_integer
- *
- * Equivalent to #scan with a [+-]?\d+ pattern, and returns an Integer or nil.
- *
- * The scanned string must be encoded with an ASCII compatible encoding, otherwise
- * Encoding::CompatibilityError will be raised.
- */
 static VALUE
-strscan_scan_integer(VALUE self)
+strscan_parse_integer(struct strscanner *p, int base, long len)
 {
-    char *ptr, *buffer;
-    long len = 0;
     VALUE buffer_v, integer;
+
+    char *buffer = RB_ALLOCV_N(char, buffer_v, len + 1);
+
+    MEMCPY(buffer, CURPTR(p), char, len);
+    buffer[len] = '\0';
+    integer = rb_cstr2inum(buffer, base);
+    RB_ALLOCV_END(buffer_v);
+    p->curr += len;
+    return integer;
+}
+
+static VALUE
+strscan_scan_base10_integer(VALUE self)
+{
+    char *ptr;
+    long len = 0;
     struct strscanner *p;
 
     GET_SCANNER(self, p);
@@ -1302,25 +1306,60 @@ strscan_scan_integer(VALUE self)
         len++;
     }
 
-    if (!isdigit(ptr[len])) {
+    if (!rb_isdigit(ptr[len])) {
         return Qnil;
     }
 
     MATCHED(p);
     p->prev = p->curr;
 
-    while (len < remaining_len && isdigit(ptr[len])) {
+    while (len < remaining_len && rb_isdigit(ptr[len])) {
         len++;
     }
 
-    buffer = RB_ALLOCV_N(char, buffer_v, len + 1);
+    return strscan_parse_integer(p, 10, len);
+}
 
-    MEMCPY(buffer, CURPTR(p), char, len);
-    buffer[len] = '\0';
-    integer = rb_cstr2inum(buffer, 10);
-    RB_ALLOCV_END(buffer_v);
-    p->curr += len;
-    return integer;
+static VALUE
+strscan_scan_base16_integer(VALUE self)
+{
+    char *ptr;
+    long len = 0;
+    struct strscanner *p;
+
+    GET_SCANNER(self, p);
+    CLEAR_MATCH_STATUS(p);
+
+    rb_must_asciicompat(p->str);
+
+    ptr = CURPTR(p);
+
+    long remaining_len = S_RESTLEN(p);
+
+    if (remaining_len <= 0) {
+        return Qnil;
+    }
+
+    if (ptr[len] == '-' || ptr[len] == '+') {
+        len++;
+    }
+
+    if ((remaining_len >= (len + 2)) && ptr[len] == '0' && ptr[len + 1] == 'x') {
+        len += 2;
+    }
+
+    if (len >= remaining_len || !rb_isxdigit(ptr[len])) {
+        return Qnil;
+    }
+
+    MATCHED(p);
+    p->prev = p->curr;
+
+    while (len < remaining_len && rb_isxdigit(ptr[len])) {
+        len++;
+    }
+
+    return strscan_parse_integer(p, 16, len);
 }
 
 /*
@@ -2261,7 +2300,8 @@ Init_strscan(void)
     rb_define_method(StringScanner, "peek_byte",   strscan_peek_byte,   0);
     rb_define_method(StringScanner, "peep",        strscan_peep,        1);
 
-    rb_define_method(StringScanner, "scan_integer", strscan_scan_integer, 0);
+    rb_define_private_method(StringScanner, "scan_base10_integer", strscan_scan_base10_integer, 0);
+    rb_define_private_method(StringScanner, "scan_base16_integer", strscan_scan_base16_integer, 0);
 
     rb_define_method(StringScanner, "unscan",      strscan_unscan,      0);
 
@@ -2290,4 +2330,6 @@ Init_strscan(void)
     rb_define_method(StringScanner, "fixed_anchor?", strscan_fixed_anchor_p, 0);
 
     rb_define_method(StringScanner, "named_captures", strscan_named_captures, 0);
+
+    rb_require("strscan/strscan");
 }

ext/strscan/strscan.gemspec

@@ -19,14 +19,17 @@ Gem::Specification.new do |s|
   files = [
     "COPYING",
     "LICENSE.txt",
+    "lib/strscan/strscan.rb"
   ]
+
+  s.require_paths = %w{lib}
+
   if RUBY_ENGINE == "jruby"
-    s.require_paths = %w{ext/jruby/lib lib}
-    files << "ext/jruby/lib/strscan.rb"
     files << "lib/strscan.jar"
+    files << "ext/jruby/lib/strscan.rb"
+    s.require_paths += %w{ext/jruby/lib}
     s.platform = "java"
   else
-    s.require_paths = %w{lib}
     files << "ext/strscan/extconf.rb"
     files << "ext/strscan/strscan.c"
     s.rdoc_options << "-idoc"

test/strscan/test_stringscanner.rb

@@ -945,6 +945,81 @@ module StringScannerTests
       s.scan_integer
     end
   end
+
+  def test_scan_integer_base_16
+    omit "scan_integer isn't implemented on TruffleRuby yet" if RUBY_ENGINE == "truffleruby"
+
+    s = create_string_scanner('0')
+    assert_equal 0x0, s.scan_integer(base: 16)
+    assert_equal 1, s.pos
+    assert_predicate s, :matched?
+
+    s = create_string_scanner('abc')
+    assert_equal 0xabc, s.scan_integer(base: 16)
+    assert_equal 3, s.pos
+    assert_predicate s, :matched?
+
+    s = create_string_scanner('123abc')
+    assert_equal 0x123abc, s.scan_integer(base: 16)
+    assert_equal 6, s.pos
+    assert_predicate s, :matched?
+
+    s = create_string_scanner('0x123abc')
+    assert_equal 0x123abc, s.scan_integer(base: 16)
+    assert_equal 8, s.pos
+    assert_predicate s, :matched?
+
+    s = create_string_scanner('0x123ABC')
+    assert_equal 0x123abc, s.scan_integer(base: 16)
+    assert_equal 8, s.pos
+    assert_predicate s, :matched?
+
+    s = create_string_scanner('-0x123ABC')
+    assert_equal -0x123abc, s.scan_integer(base: 16)
+    assert_equal 9, s.pos
+    assert_predicate s, :matched?
+
+    s = create_string_scanner('+0x123ABC')
+    assert_equal +0x123abc, s.scan_integer(base: 16)
+    assert_equal 9, s.pos
+    assert_predicate s, :matched?
+
+    s = create_string_scanner('0x')
+    assert_nil s.scan_integer(base: 16)
+    assert_equal 0, s.pos
+    refute_predicate s, :matched?
+
+    s = create_string_scanner('-0x')
+    assert_nil s.scan_integer(base: 16)
+    assert_equal 0, s.pos
+    refute_predicate s, :matched?
+
+    s = create_string_scanner('+0x')
+    assert_nil s.scan_integer(base: 16)
+    assert_equal 0, s.pos
+    refute_predicate s, :matched?
+
+    s = create_string_scanner('-123abc')
+    assert_equal -0x123abc, s.scan_integer(base: 16)
+    assert_equal 7, s.pos
+    assert_predicate s, :matched?
+
+    s = create_string_scanner('+123')
+    assert_equal 0x123, s.scan_integer(base: 16)
+    assert_equal 4, s.pos
+    assert_predicate s, :matched?
+
+    s = create_string_scanner('-abc')
+    assert_equal -0xabc, s.scan_integer(base: 16)
+    assert_equal 4, s.pos
+    assert_predicate s, :matched?
+
+    huge_integer = 'F' * 2_000
+    s = create_string_scanner(huge_integer)
+    assert_equal huge_integer.to_i(16), s.scan_integer(base: 16)
+    assert_equal 2_000, s.pos
+    assert_predicate s, :matched?
+  end
 end
 
 class TestStringScanner < Test::Unit::TestCase