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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