Re: Proposal: add new API to stringinfo - Mailing list pgsql-hackers

>> With opinions from Michael and David , what about following additional
>> APIs?
>>
>> #define STRINGINFO_DEFAULT_SIZE 1024 /* default initial allocation size
>> #*/
>> #define STRINGINFO_SMALL_SIZE 64 /* small initial allocation size */
>>
>> #define makeStringInfo makeStringInfoExtended(STRINGINFO_DEFAULT_SIZE)
>> #define initStringInfo(str) initStringInfoExtended(str,
>> #STRINGINFO_DEFAULT_SIZE)
>>
>> extern StringInfo makeStringInfoExtended(int initsize);
>> extern void initStringInfoExtended(StringInfo str, int initsize);
>>
> 
> 
> Seems like a good idea.

Thanks.

> Minor nit: the definition of the macro should contain parentheses, like so:
> #define makeStringInfo()   ....

Indeed. Thanks for pointing it out.

Attached is the patch for this.

Best reagards,
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp
From fe0f556264d0d25469da93896c312d7957936531 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sat, 4 Jan 2025 13:27:50 +0900
Subject: [PATCH v1] Add new StringInfo APIs.

Previously StringInfo only provided APIs with fixed initial memory
allocation size for the data buffer: 1024 bytes. This is inappropreate
for some callers that need less memory buffer. To fix this, new APIs
that accept the initial memory allocation size parameter are added:

extern StringInfo makeStringInfoExtended(int initsize);
extern void initStringInfoExtended(StringInfo str, int initsize);

Existing APIs (makeStringInfo() and initStringInfo()) now become
macros to call makeStringInfoExtended() and initStringInfoExtended()
respectively. This means that callers of makeStringInfo() and
initStringInfo() need to be recompiled.
---
 src/common/stringinfo.c      | 23 +++++++++++++----------
 src/include/lib/stringinfo.h | 34 +++++++++++++++++++++++++++++++---
 2 files changed, 44 insertions(+), 13 deletions(-)

diff --git a/src/common/stringinfo.c b/src/common/stringinfo.c
index 55d2fbb864d..6838f9659aa 100644
--- a/src/common/stringinfo.c
+++ b/src/common/stringinfo.c
@@ -30,35 +30,38 @@
 
 
 /*
- * makeStringInfo
+ * makeStringInfoExtended(int initsize)
  *
  * Create an empty 'StringInfoData' & return a pointer to it.
+ * The initial memory allocation size is specified by 'initsize'.
  */
 StringInfo
-makeStringInfo(void)
+makeStringInfoExtended(int initsize)
 {
     StringInfo    res;
 
+    Assert(initsize > 0);
+
     res = (StringInfo) palloc(sizeof(StringInfoData));
 
-    initStringInfo(res);
+    initStringInfoExtended(res, initsize);
 
     return res;
 }
 
 /*
- * initStringInfo
+ * initStringInfoExtended
  *
- * Initialize a StringInfoData struct (with previously undefined contents)
- * to describe an empty string.
+ * Initialize a StringInfoData struct (with previously undefined contents).
+ * The initial memory allocation size is specified by 'initsize'.
  */
 void
-initStringInfo(StringInfo str)
+initStringInfoExtended(StringInfo str, int initsize)
 {
-    int            size = 1024;    /* initial default buffer size */
+    Assert(initsize > 0);
 
-    str->data = (char *) palloc(size);
-    str->maxlen = size;
+    str->data = (char *) palloc(initsize);
+    str->maxlen = initsize;
     resetStringInfo(str);
 }
 
diff --git a/src/include/lib/stringinfo.h b/src/include/lib/stringinfo.h
index 335208a9fda..37e91b73714 100644
--- a/src/include/lib/stringinfo.h
+++ b/src/include/lib/stringinfo.h
@@ -55,11 +55,15 @@ typedef StringInfoData *StringInfo;
 
 
 /*------------------------
- * There are four ways to create a StringInfo object initially:
+ * There are six ways to create a StringInfo object initially:
  *
  * StringInfo stringptr = makeStringInfo();
  *        Both the StringInfoData and the data buffer are palloc'd.
  *
+ * StringInfo stringptr = makeStringInfoExtended(initsize);
+ *        Same as makeStringInfo except the data buffer is allocated
+ *        with size 'initsize'.
+ *
  * StringInfoData string;
  * initStringInfo(&string);
  *        The data buffer is palloc'd but the StringInfoData is just local.
@@ -67,6 +71,11 @@ typedef StringInfoData *StringInfo;
  *        only live as long as the current routine.
  *
  * StringInfoData string;
+ * initStringInfoExtended(&string, initsize);
+ *        Same as initStringInfo except the data buffer is allocated
+ *        with size 'initsize'.
+ *
+ * StringInfoData string;
  * initReadOnlyStringInfo(&string, existingbuf, len);
  *        The StringInfoData's data field is set to point directly to the
  *        existing buffer and the StringInfoData's len is set to the given len.
@@ -100,18 +109,37 @@ typedef StringInfoData *StringInfo;
  *-------------------------
  */
 
+#define STRINGINFO_DEFAULT_SIZE 1024    /* default initial allocation size */
+#define STRINGINFO_SMALL_SIZE 64    /* small initial allocation size */
+
 /*------------------------
  * makeStringInfo
  * Create an empty 'StringInfoData' & return a pointer to it.
  */
-extern StringInfo makeStringInfo(void);
+#define makeStringInfo()    makeStringInfoExtended(STRINGINFO_DEFAULT_SIZE)
+
+/*------------------------
+ * makeStringInfoExtended
+ * Create an empty 'StringInfoData' & return a pointer to it.
+ * The data buffer is allocated with size 'initsize'.
+ */
+extern StringInfo makeStringInfoExtended(int initsize);
 
 /*------------------------
  * initStringInfo
  * Initialize a StringInfoData struct (with previously undefined contents)
  * to describe an empty string.
  */
-extern void initStringInfo(StringInfo str);
+#define initStringInfo(str) \
+    initStringInfoExtended(str, STRINGINFO_DEFAULT_SIZE)
+
+/*------------------------
+ * initStringInfoExtended
+ * Initialize a StringInfoData struct (with previously undefined contents)
+ * to describe an empty string.
+ * The data buffer is allocated with size 'initsize'.
+ */
+extern void initStringInfoExtended(StringInfo str, int initsize);
 
 /*------------------------
  * initReadOnlyStringInfo
-- 
2.25.1