《C语言的科学与艺术》_头文件

/* * File: strlib.c * Version: 1.0 * Last modified on Fri Jul 15 14:10:41 1994 by eroberts * ----------------------------------------------------- * This file implements the strlib.h interface. */ /* * General implementation notes: * ----------------------------- * This module implements the strlib library by mapping all * functions into the appropriate calls to the ANSI <string.h> * interface. The implementations of the individual functions * are all quite simple and do not require individual comments. * For descriptions of the behavior of each function, see the * interface. */ #include <stdio.h> #include <string.h> #include <ctype.h> #include "genlib.h" #include "strlib.h" /* * Constant: MaxDigits * ------------------- * This constant must be larger than the maximum * number of digits that can appear in a number. */ #define MaxDigits 30 /* Private function prototypes */ static string CreateString(int len); /* Section 1 -- Basic string operations */ string Concat(string s1, string s2) { string s; int len1, len2; if (s1 == NULL || s2 == NULL) { Error("NULL string passed to Concat"); } len1 = strlen(s1); len2 = strlen(s2); s = CreateString(len1 + len2); strcpy(s, s1); strcpy(s + len1, s2); return (s); } char IthChar(string s, int i) { int len; if (s == NULL) Error("NULL string passed to IthChar"); len = strlen(s); if (i < 0 || i > len) { Error("Index outside of string range in IthChar"); } return (s[i]); } string SubString(string s, int p1, int p2) { int len; string result; if (s == NULL) Error("NULL string passed to SubString"); len = strlen(s); if (p1 < 0) p1 = 0; if (p2 >= len) p2 = len - 1; len = p2 - p1 + 1; if (len < 0) len = 0; result = CreateString(len); strncpy(result, s + p1, len); result[len] = '\0'; return (result); } string CharToString(char ch) { string result; result = CreateString(1); result[0] = ch; result[1] = '\0'; return (result); } int StringLength(string s) { if (s == NULL) Error("NULL string passed to StringLength"); return (strlen(s)); } string CopyString(string s) { string newstr; if (s == NULL) Error("NULL string passed to CopyString"); newstr = CreateString(strlen(s)); strcpy(newstr, s); return (newstr); } /* Section 2 -- String comparison functions */ bool StringEqual(string s1, string s2) { if (s1 == NULL || s2 == NULL) { Error("NULL string passed to StringEqual"); } return (strcmp(s1, s2) == 0); } int StringCompare(string s1, string s2) { if (s1 == NULL || s2 == NULL) { Error("NULL string passed to StringCompare"); } return (strcmp(s1, s2)); } /* Section 3 -- Search functions */ int FindChar(char ch, string text, int start) { char *cptr; if (text == NULL) Error("NULL string passed to FindChar"); if (start < 0) start = 0; if (start > strlen(text)) return (-1); cptr = strchr(text + start, ch); if (cptr == NULL) return (-1); return ((int) (cptr - text)); } int FindString(string str, string text, int start) { char *cptr; if (str == NULL) Error("NULL pattern string in FindString"); if (text == NULL) Error("NULL text string in FindString"); if (start < 0) start = 0; if (start > strlen(text)) return (-1); cptr = strstr(text + start, str); if (cptr == NULL) return (-1); return ((int) (cptr - text)); } /* Section 4 -- Case-conversion functions */ string ConvertToLowerCase(string s) { string result; int i; if (s == NULL) { Error("NULL string passed to ConvertToLowerCase"); } result = CreateString(strlen(s)); for (i = 0; s[i] != '\0'; i++) result[i] = tolower(s[i]); result[i] = '\0'; return (result); } string ConvertToUpperCase(string s) { string result; int i; if (s == NULL) { Error("NULL string passed to ConvertToUpperCase"); } result = CreateString(strlen(s)); for (i = 0; s[i] != '\0'; i++) result[i] = toupper(s[i]); result[i] = '\0'; return (result); } /* Section 5 -- Functions for converting numbers to strings */ string IntegerToString(int n) { char buffer[MaxDigits]; sprintf(buffer, "%d", n); return (CopyString(buffer)); } int StringToInteger(string s) { int result; char dummy; if (s == NULL) { Error("NULL string passed to StringToInteger"); } if (sscanf(s, " %d %c", &result, &dummy) != 1) { Error("StringToInteger called on illegal number %s", s); } return (result); } string RealToString(double d) { char buffer[MaxDigits]; sprintf(buffer, "%G", d); return (CopyString(buffer)); } double StringToReal(string s) { double result; char dummy; if (s == NULL) Error("NULL string passed to StringToReal"); if (sscanf(s, " %lg %c", &result, &dummy) != 1) { Error("StringToReal called on illegal number %s", s); } return (result); } /* Private functions */ /* * Function: CreateString * Usage: s = CreateString(len); * ----------------------------- * This function dynamically allocates space for a string of * len characters, leaving room for the null character at the * end. */ static string CreateString(int len) { return ((string) GetBlock(len + 1)); }