From 9dcdffb8bf8a3654fd78bf1a58b30c8e13888a7a Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Sun, 9 Jul 2023 18:45:51 +0900
Subject: [PATCH] Make the string index functions closer to symmetric

So that irregular parts may be more noticeable.
---
 string.c | 84 +++++++++++++++++++++-----------------------------------
 1 file changed, 32 insertions(+), 52 deletions(-)

diff --git a/string.c b/string.c
index c34a1808793aef..af0668e4b25dc7 100644
--- a/string.c
+++ b/string.c
@@ -3809,6 +3809,7 @@ strseq_core(const char *str_ptr, const char *str_ptr_end, long str_len,
 
 /* found index in byte */
 #define rb_str_index(str, sub, offset) rb_strseq_index(str, sub, offset, 0)
+#define rb_str_byteindex(str, sub, offset) rb_strseq_index(str, sub, offset, 1)
 
 static long
 rb_strseq_index(VALUE str, VALUE sub, long offset, int in_byte)
@@ -3866,33 +3867,24 @@ rb_str_index_m(int argc, VALUE *argv, VALUE str)
     long pos;
 
     if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
+        long slen = str_strlen(str, enc); /* str's enc */
         pos = NUM2LONG(initpos);
-    }
-    else {
-        pos = 0;
-    }
-    if (pos < 0) {
-        pos += str_strlen(str, NULL);
-        if (pos < 0) {
+        if (pos < 0 ? (pos += slen) < 0 : pos > slen) {
             if (RB_TYPE_P(sub, T_REGEXP)) {
                 rb_backref_set(Qnil);
             }
             return Qnil;
         }
     }
+    else {
+        pos = 0;
+    }
 
     if (RB_TYPE_P(sub, T_REGEXP)) {
-        if (pos > str_strlen(str, NULL)) {
-            rb_backref_set(Qnil);
-            return Qnil;
-        }
         pos = str_offset(RSTRING_PTR(str), RSTRING_END(str), pos,
                          enc, single_byte_optimizable(str));
 
-        if (rb_reg_search(sub, str, pos, 0) < 0) {
-            return Qnil;
-        }
-        else {
+        if (rb_reg_search(sub, str, pos, 0) >= 0) {
             VALUE match = rb_backref_get();
             struct re_registers *regs = RMATCH_REGS(match);
             pos = rb_str_sublen(str, BEG(0));
@@ -3902,11 +3894,12 @@ rb_str_index_m(int argc, VALUE *argv, VALUE str)
     else {
         StringValue(sub);
         pos = rb_str_index(str, sub, pos);
-        pos = rb_str_sublen(str, pos);
+        if (pos >= 0) {
+            pos = rb_str_sublen(str, pos);
+            return LONG2NUM(pos);
+        }
     }
-
-    if (pos == -1) return Qnil;
-    return LONG2NUM(pos);
+    return Qnil;
 }
 
 /* Ensure that the given pos is a valid character boundary.
@@ -3977,10 +3970,7 @@ rb_str_byteindex_m(int argc, VALUE *argv, VALUE str)
     if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
         long slen = RSTRING_LEN(str);
         pos = NUM2LONG(initpos);
-        if (pos < 0) {
-            pos += slen;
-        }
-        if (pos < 0 || pos > slen) {
+        if (pos < 0 ? (pos += slen) < 0 : pos > slen) {
             if (RB_TYPE_P(sub, T_REGEXP)) {
                 rb_backref_set(Qnil);
             }
@@ -3994,10 +3984,7 @@ rb_str_byteindex_m(int argc, VALUE *argv, VALUE str)
     str_ensure_byte_pos(str, pos);
 
     if (RB_TYPE_P(sub, T_REGEXP)) {
-        if (rb_reg_search(sub, str, pos, 0) < 0) {
-            return Qnil;
-        }
-        else {
+        if (rb_reg_search(sub, str, pos, 0) >= 0) {
             VALUE match = rb_backref_get();
             struct re_registers *regs = RMATCH_REGS(match);
             pos = BEG(0);
@@ -4006,11 +3993,10 @@ rb_str_byteindex_m(int argc, VALUE *argv, VALUE str)
     }
     else {
         StringValue(sub);
-        pos = rb_strseq_index(str, sub, pos, 1);
+        pos = rb_str_byteindex(str, sub, pos);
+        if (pos >= 0) return LONG2NUM(pos);
     }
-
-    if (pos == -1) return Qnil;
-    return LONG2NUM(pos);
+    return Qnil;
 }
 
 #ifdef HAVE_MEMRCHR
@@ -4163,20 +4149,17 @@ static VALUE
 rb_str_rindex_m(int argc, VALUE *argv, VALUE str)
 {
     VALUE sub;
-    VALUE vpos;
+    VALUE initpos;
     rb_encoding *enc = STR_ENC_GET(str);
     long pos, len = str_strlen(str, enc); /* str's enc */
 
-    if (rb_scan_args(argc, argv, "11", &sub, &vpos) == 2) {
-        pos = NUM2LONG(vpos);
-        if (pos < 0) {
-            pos += len;
-            if (pos < 0) {
-                if (RB_TYPE_P(sub, T_REGEXP)) {
-                    rb_backref_set(Qnil);
-                }
-                return Qnil;
+    if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
+        pos = NUM2LONG(initpos);
+        if (pos < 0 && (pos += len) < 0) {
+            if (RB_TYPE_P(sub, T_REGEXP)) {
+                rb_backref_set(Qnil);
             }
+            return Qnil;
         }
         if (pos > len) pos = len;
     }
@@ -4302,19 +4285,16 @@ static VALUE
 rb_str_byterindex_m(int argc, VALUE *argv, VALUE str)
 {
     VALUE sub;
-    VALUE vpos;
+    VALUE initpos;
     long pos, len = RSTRING_LEN(str);
 
-    if (rb_scan_args(argc, argv, "11", &sub, &vpos) == 2) {
-        pos = NUM2LONG(vpos);
-        if (pos < 0) {
-            pos += len;
-            if (pos < 0) {
-                if (RB_TYPE_P(sub, T_REGEXP)) {
-                    rb_backref_set(Qnil);
-                }
-                return Qnil;
+    if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
+        pos = NUM2LONG(initpos);
+        if (pos < 0 && (pos += len) < 0) {
+            if (RB_TYPE_P(sub, T_REGEXP)) {
+                rb_backref_set(Qnil);
             }
+            return Qnil;
         }
         if (pos > len) pos = len;
     }
@@ -5570,7 +5550,7 @@ static long
 rb_pat_search(VALUE pat, VALUE str, long pos, int set_backref_str)
 {
     if (BUILTIN_TYPE(pat) == T_STRING) {
-        pos = rb_strseq_index(str, pat, pos, 1);
+        pos = rb_str_byteindex(str, pat, pos);
         if (set_backref_str) {
             if (pos >= 0) {
                 str = rb_str_new_frozen_String(str);