C语言去除相邻重复字符函数的实现方法

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C语言去除相邻重复字符函数的实现方法

字符去重函数

功能：去重字符串相邻重复的字符，不相邻的不用去重

参数：

arg1 -- 输入字符串
arg2 -- 字符串开始位置
arg3 -- 字符串结束位置

要求：

输入参数为arg1时，对这个字符串去重
输入参数为arg1，arg2时，从arg2位置到字符串结束，去重
输入参数为arg1，arg2，arg3时，从arg2到arg3位置，去重

src/include/catalog/pg_proc.h

DATA(insert OID = 6669 ( remove_dup_char PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 25 "25" _null_ _null_ _null_ _null_ _null_ remove_dup_char_arg1 _null_ _null_ _null_ ));
DESCR("Remove duplicate characters.");
DATA(insert OID = 6670 ( remove_dup_char PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 25 "25 23" _null_ _null_ _null_ _null_ _null_ remove_dup_char_arg2 _null_ _null_ _null_ ));
DESCR("Remove duplicate characters.");
DATA(insert OID = 6671 ( remove_dup_char PGNSP PGUID 12 1 0 0 0 f f f f t f i 3 0 25 "25 23 23" _null_ _null_ _null_ _null_ _null_ remove_dup_char_arg3 _null_ _null_ _null_ ));
DESCR("Remove duplicate characters.");

src/backend/utils/adt/myfuncs.c

/* 
 * Remove duplicate characters 
 * author:young
 */
Datum 
remove_dup_char_arg1 (PG_FUNCTION_ARGS)
{
 int n = 0;
 text *arg0 = PG_GETARG_TEXT_P(0);

 char *str = text_to_cstring(arg0);
 n = strlen(str);

 remove_dup(str, 0, n);

 PG_RETURN_TEXT_P(cstring_to_text(str));
}

Datum 
remove_dup_char_arg2 (PG_FUNCTION_ARGS)
{
 int n = 0;
 text *arg0 = PG_GETARG_TEXT_P(0);
 int32 arg1 = PG_GETARG_INT32(1);

 char *str = text_to_cstring(arg0);
 n = strlen(str);

 if (!(1 <= arg1 && arg1 <= n))
 {
 ereport(ERROR,
  (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
  errmsg("out of range")));
 }

 remove_dup(str, arg1 - 1, n);

 PG_RETURN_TEXT_P(cstring_to_text(str));
}

Datum 
remove_dup_char_arg3 (PG_FUNCTION_ARGS)
{
 int n = 0;
 text *arg0 = PG_GETARG_TEXT_P(0);
 int32 arg1 = PG_GETARG_INT32(1);
 int32 arg2 = PG_GETARG_INT32(2);

 char *str = text_to_cstring(arg0);
 n = strlen(str);

 if (!(1 <= arg1 && arg1 <= arg2 && arg2 <= n))
 {
 ereport(ERROR,
  (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
  errmsg("out of range")));
 }

 remove_dup(str, arg1 - 1, arg2 - 1);

 PG_RETURN_TEXT_P(cstring_to_text(str));
}

void 
remove_dup(char *str, int start, int end)
{
 int i = start, k = start;

 for (i = start; i <= end; i++) 
 {
 if (str[i + 1] && str[i + 1] == str[i] && i + 1 <= end)
 {
  k++;
 } 
 else 
 {
  str[i-k] = str[i];
 }   
 }
 str[i-k] = '\0';
}

比较繁琐，再做一下修改，三个函数放到一个中

src/include/catalog/pg_proc.h

DATA(insert OID = 6669 ( remove_dup_char PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 25 "25" _null_ _null_ _null_ _null_ _null_ remove_dup_char _null_ _null_ _null_ ));
DESCR("Remove duplicate characters.");
DATA(insert OID = 6670 ( remove_dup_char PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 25 "25 23" _null_ _null_ _null_ _null_ _null_ remove_dup_char _null_ _null_ _null_ ));
DESCR("Remove duplicate characters.");
DATA(insert OID = 6671 ( remove_dup_char PGNSP PGUID 12 1 0 0 0 f f f f t f i 3 0 25 "25 23 23" _null_ _null_ _null_ _null_ _null_ remove_dup_char _null_ _null_ _null_ ));
DESCR("Remove duplicate characters.");

src/backend/utils/adt/myfuncs.c

添加定义：

#define PG_GETARG_IF_EXISTS(n, type, defval) \
 ((PG_NARGS() > (n) && !PG_ARGISNULL(n)) ? PG_GETARG_##type(n) : (defval))

修改方法：

/* 
 * Remove duplicate characters 
 * author:yangjie
 */
Datum 
remove_dup_char (PG_FUNCTION_ARGS)
{
 text *arg0 = PG_GETARG_IF_EXISTS(0, TEXT_P, NULL);
 int32 arg1 = PG_GETARG_IF_EXISTS(1, INT32, 0);
 int32 arg2 = PG_GETARG_IF_EXISTS(2, INT32, 0);
 int n = 0;

 char *str = text_to_cstring(arg0);
 n = strlen(str);

 if(PG_NARGS() == 1)
 {
 remove_dup(str, 0, n);
 }

 if(PG_NARGS() == 2)
 {
 if (!(1 <= arg1 && arg1 <= n))
 {
  ereport(ERROR,
  (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
  errmsg("out of range")));
 }
 remove_dup(str, arg1 - 1, n);
 }

 if(PG_NARGS() == 3)
 {
 if (!(1 <= arg1 && arg1 <= arg2 && arg2 <= n))
 {
  ereport(ERROR,
  (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
  errmsg("out of range")));
 }
 remove_dup(str, arg1 - 1, arg2 - 1);
 }

 PG_RETURN_TEXT_P(cstring_to_text(str));
}

再修改一下，如果有输入参数就用没有就用默认值最后再去重处理减少代码重用

/* 
 * Remove duplicate characters 
 * author:yangjie
 */
Datum 
remove_dup_char (PG_FUNCTION_ARGS)
{
 text *arg0 = PG_GETARG_IF_EXISTS(0, TEXT_P, NULL);
 int n = 0;
 char *str = text_to_cstring(arg0);
 n = strlen(str);
 int32 arg1 = PG_GETARG_IF_EXISTS(1, INT32, 0);
 int32 arg2 = PG_GETARG_IF_EXISTS(2, INT32, n);
 
 if (!(1 <= arg1 && arg1 <= n))
 {
 ereport(ERROR,
  (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
  errmsg("1 <= arg1 && arg1 <= n")));
 }

 if (!(1 <= arg1 && arg1 <= arg2 && arg2 <= n))
 {
 ereport(ERROR,
  (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
  errmsg("1 <= arg1 && arg1 <= arg2 && arg2 <= n")));
 }

 remove_dup(str, arg1, arg2);
 
 PG_RETURN_TEXT_P(cstring_to_text(str));
}

void 
remove_dup(char *str, int start, int end)
{
 int i = start -1, k = start - 1;

 for (i = start - 1; i <= end - 1; i++) 
 {
 if (str[i + 1] && str[i + 1] == str[i] && i + 1 <= end - 1)
 {
  k++;
 } 
 else 
 {
  str[i-k] = str[i];
 }   
 }
 str[i-k] = '\0';
}

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