由于ngx_str_t为非NULL结尾的函数，且网络请求中有大量忽略大小写的需求，所以nginx内部封装了许多字符串操作相关的函数，函数名称极其相识，且使用时有有些约定，特此整理。
赋值&拷贝
#define ngx_string(str) { sizeof(str) - 1, (u_char *) str }
#define ngx_null_string { 0, NULL }
#define ngx_str_set(str, text) (str)->len = sizeof(text) - 1; (str)->data = (u_char *) text
#define ngx_str_null(str) (str)->len = 0; (str)->data = NULL
//ngx_string与ngx_null_string常用于变量初始化
//ngx_str_set与ngx_str_null常用于变量赋值
#define ngx_memzero(buf, n) (void) memset(buf, 0, n)
#define ngx_memset(buf, c, n) (void) memset(buf, c, n)
#define ngx_memcpy(dst, src, n) (void) memcpy(dst, src, n)
#define ngx_cpymem(dst, src, n) (((u_char *) memcpy(dst, src, n)) + (n))
#define ngx_copy ngx_cpymem
//ngx_cpymem返回dst的结尾位置
#define ngx_memmove(dst, src, n) (void) memmove(dst, src, n)
#define ngx_movemem(dst, src, n) (((u_char *) memmove(dst, src, n)) + (n))
//ngx_movemem返回dst的结尾位置
u_char *ngx_cpystrn(u_char *dst, u_char *src, size_t n);
//字符串赋值，且dst为NULL结尾
u_char *ngx_pstrdup(ngx_pool_t *pool, ngx_str_t *src);
//从pool内申请空间，并使用src赋值，不保证NULL结尾
字符串长度
#define ngx_strlen(s) strlen((const char *) s) size_t ngx_strnlen(u_char *p, size_t n); //返回第一个'\0'或者n
大小写转换
#define ngx_tolower(c) (u_char) ((c >= 'A' && c <= 'Z') ? (c | 0x20) : c) #define ngx_toupper(c) (u_char) ((c >= 'a' && c <= 'z') ? (c & ~0x20) : c) void ngx_strlow(u_char *dst, u_char *src, size_t n);
字符串比对
#define ngx_strncmp(s1, s2, n) strncmp((const char *) s1, (const char *) s2, n) //调用前需要保证s1与s2长度一致 #define ngx_strcmp(s1, s2) strcmp((const char *) s1, (const char *) s2) //s1与s2都需要NULL结尾 ngx_int_t ngx_rstrncmp(u_char *s1, u_char *s2, size_t n); //调用前需要保证s1与s2长度一致，使用较少，常用ngx_strncmp #define ngx_memcmp(s1, s2, n) memcmp((const char *) s1, (const char *) s2, n) ngx_int_t ngx_strcasecmp(u_char *s1, u_char *s2); //忽略大小写比对，s1需要NULL结尾，调用前需要保证s1与s2长度一致 ngx_int_t ngx_strncasecmp(u_char *s1, u_char *s2, size_t n); //忽略大小写比对，调用前需要保证s1与s2长度一致 ngx_int_t ngx_rstrncasecmp(u_char *s1, u_char *s2, size_t n); //忽略大小写比对，调用前需要保证s1与s2长度一致 ngx_int_t ngx_memn2cmp(u_char *s1, u_char *s2, size_t n1, size_t n2); //内部判断长度相等 ngx_int_t ngx_dns_strcmp(u_char *s1, u_char *s2); //忽略大小写比对，且忽略最后的'.'字符 ngx_int_t ngx_filename_cmp(u_char *s1, u_char *s2, size_t n); //根据操作系统，选择是否忽略大小写，且忽略最后的'/'字符
字符串搜索
#define ngx_strchr(s1, c) strchr((const char *) s1, (int) c) //字符搜索s1默认NULL结尾 static ngx_inline u_char * ngx_strlchr(u_char *p, u_char *last, u_char c); //字符搜索 u_char *ngx_strnstr(u_char *s1, char *s2, size_t n); //在s1中搜索子串s2，s2需要NULL结尾，n为s1长度 u_char *ngx_strstrn(u_char *s1, char *s2, size_t n); //在s1中搜索子串s2，s1需要NULL结尾，n为s2长度-1 u_char *ngx_strcasestrn(u_char *s1, char *s2, size_t n); //忽略大小写，在s1中搜索子串s2，s1需要NULL结尾，n为s2长度-1 u_char *ngx_strlcasestrn(u_char *s1, u_char *last, u_char *s2, size_t n); //忽略大小写，在[s1,last]中搜索子串s2，n为s2长度-1
字符串格式化
u_char * ngx_cdecl ngx_sprintf(u_char *buf, const char *fmt, ...); //字符串格式化，外部保证buf大小 u_char * ngx_cdecl ngx_snprintf(u_char *buf, size_t max, const char *fmt, ...); u_char * ngx_cdecl ngx_slprintf(u_char *buf, u_char *last, const char *fmt, ...); u_char *ngx_vslprintf(u_char *buf, u_char *last, const char *fmt, va_list args); //ngx_sprintf、ngx_snprintf、ngx_slprintf的内部函数，用于不定长参数的函数使用
字符串/数字转换
ngx_int_t ngx_atoi(u_char *line, size_t n); ngx_int_t ngx_atofp(u_char *line, size_t n, size_t point); ssize_t ngx_atosz(u_char *line, size_t n); off_t ngx_atoof(u_char *line, size_t n); time_t ngx_atotm(u_char *line, size_t n); ngx_int_t ngx_hextoi(u_char *line, size_t n); u_char *ngx_hex_dump(u_char *dst, u_char *src, size_t len);
字符串编解码
#define ngx_base64_encoded_length(len) (((len + 2) / 3) * 4) #define ngx_base64_decoded_length(len) (((len + 3) / 4) * 3) void ngx_encode_base64(ngx_str_t *dst, ngx_str_t *src); void ngx_encode_base64url(ngx_str_t *dst, ngx_str_t *src); ngx_int_t ngx_decode_base64(ngx_str_t *dst, ngx_str_t *src); ngx_int_t ngx_decode_base64url(ngx_str_t *dst, ngx_str_t *src); uint32_t ngx_utf8_decode(u_char **p, size_t n); size_t ngx_utf8_length(u_char *p, size_t n); u_char *ngx_utf8_cpystrn(u_char *dst, u_char *src, size_t n, size_t len); uintptr_t ngx_escape_uri(u_char *dst, u_char *src, size_t size, ngx_uint_t type); void ngx_unescape_uri(u_char **dst, u_char **src, size_t size, ngx_uint_t type); uintptr_t ngx_escape_html(u_char *dst, u_char *src, size_t size); uintptr_t ngx_escape_json(u_char *dst, u_char *src, size_t size);
来源：https://www.cnblogs.com/atskyline/p/8124247.html