normal	2018-07-18 17:16:18 +0900 (Wed, 18 Jul 2018)

  New Revision: 63993

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=63993

  Log:
    zlib (rb_gzreader_getc): localize and return cbuf directly
    
    No point in having a long-lived cbuf in "struct gzfile"
    since GZFILE_CBUF_CAPA is smaller than RSTRING_EMBED_LEN_MAX
    (even on 32-bit).  We can also have rb_econv_convert write
    directly to the return value instead of an intermediate buffer.
    
    This brings "struct gzfile" from 264 to 256 bytes on 64-bit
    systems to avoid taking an additional cache line.

  Modified files:
    trunk/ext/zlib/zlib.c
Index: ext/zlib/zlib.c
===================================================================
--- ext/zlib/zlib.c	(revision 63992)
+++ ext/zlib/zlib.c	(revision 63993)
@@ -2225,7 +2225,6 @@ struct gzfile { https://github.com/ruby/ruby/blob/trunk/ext/zlib/zlib.c#L2225
     rb_encoding *enc2;
     rb_econv_t *ec;
     VALUE ecopts;
-    char *cbuf;
     VALUE path;
 };
 #define GZFILE_CBUF_CAPA 10
@@ -2275,22 +2274,13 @@ gzfile_free(void *p) https://github.com/ruby/ruby/blob/trunk/ext/zlib/zlib.c#L2274
 	}
 	zstream_finalize(z);
     }
-    if (gz->cbuf) {
-	xfree(gz->cbuf);
-    }
     xfree(gz);
 }
 
 static size_t
 gzfile_memsize(const void *p)
 {
-    const struct gzfile *gz = p;
-    size_t size = sizeof(struct gzfile);
-
-    if (gz->cbuf)
-	size += GZFILE_CBUF_CAPA;
-
-    return size;
+    return sizeof(struct gzfile);
 }
 
 static const rb_data_type_t gzfile_data_type = {
@@ -2319,7 +2309,6 @@ gzfile_init(struct gzfile *gz, const str https://github.com/ruby/ruby/blob/trunk/ext/zlib/zlib.c#L2309
     gz->ec = NULL;
     gz->ecflags = 0;
     gz->ecopts = Qnil;
-    gz->cbuf = 0;
     gz->path = Qnil;
 }
 
@@ -2870,22 +2859,19 @@ gzfile_getc(struct gzfile *gz) https://github.com/ruby/ruby/blob/trunk/ext/zlib/zlib.c#L2859
     if (gz->ec && rb_enc_dummy_p(gz->enc2)) {
 	const unsigned char *ss, *sp, *se;
 	unsigned char *ds, *dp, *de;
+	VALUE cbuf = rb_enc_str_new(0, GZFILE_CBUF_CAPA, gz->enc);
 
-	if (!gz->cbuf) {
-	    gz->cbuf = ALLOC_N(char, GZFILE_CBUF_CAPA);
-	}
         ss = sp = (const unsigned char*)RSTRING_PTR(gz->z.buf);
         se = sp + ZSTREAM_BUF_FILLED(&gz->z);
-        ds = dp = (unsigned char *)gz->cbuf;
+        ds = dp = (unsigned char *)RSTRING_PTR(cbuf);
         de = (unsigned char *)ds + GZFILE_CBUF_CAPA;
         (void)rb_econv_convert(gz->ec, &sp, se, &dp, de, ECONV_PARTIAL_INPUT|ECONV_AFTER_OUTPUT);
         rb_econv_check_error(gz->ec);
 	dst = zstream_shift_buffer(&gz->z, sp - ss);
 	gzfile_calc_crc(gz, dst);
-	dst = rb_str_new(gz->cbuf, dp - ds);
-	rb_enc_associate(dst, gz->enc);
-	OBJ_TAINT(dst);
-	return dst;
+	rb_str_resize(cbuf, dp - ds);
+	OBJ_TAINT(cbuf);
+	return cbuf;
     }
     else {
 	buf = gz->z.buf;

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