From 6f8d17e43c7b9b3b8bf42df0ef1ca085080b65f0 Mon Sep 17 00:00:00 2001 From: Peter Zhu Date: Tue, 27 Sep 2022 14:50:40 -0400 Subject: [PATCH] Make string slices views rather than copies Just like commit 1c16645 for arrays, this commit changes string slices to be a view rather than a copy even if it can be allocated through VWA. --- string.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/string.c b/string.c index b9c567cbe2..bdab6fa143 100644 --- a/string.c +++ b/string.c @@ -2802,18 +2802,20 @@ str_subseq(VALUE str, long beg, long len) { VALUE str2; - if (!STR_EMBEDDABLE_P(len, TERM_LEN(str)) && - SHARABLE_SUBSTRING_P(beg, len, RSTRING_LEN(str))) { - str2 = rb_str_new_shared(str); + const long rstring_embed_capa_max = ((sizeof(struct RString) - offsetof(struct RString, as.embed.ary)) / sizeof(char)) - 1; + + if (!SHARABLE_SUBSTRING_P(beg, len, RSTRING_LEN(str)) || + len <= rstring_embed_capa_max) { + str2 = rb_str_new(RSTRING_PTR(str) + beg, len); + RB_GC_GUARD(str); + } + else { + str2 = str_new_shared(rb_cString, str); RSTRING(str2)->as.heap.ptr += beg; if (RSTRING(str2)->as.heap.len > len) { RSTRING(str2)->as.heap.len = len; } } - else { - str2 = rb_str_new(RSTRING_PTR(str) + beg, len); - RB_GC_GUARD(str); - } return str2; }