由於ngx_str_t為非NULL結尾的函數，且網絡請求中有大量忽略大小寫的需求，所以nginx內部封裝了許多字符串操作相關的函數，函數名稱極其相識，且使用時有有些約定，特此整理。
賦值&拷貝
#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與ngx_null_string常用於變量初始化
//ngx_str_set與ngx_str_null常用於變量賦值
#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的結尾位置
#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的結尾位置
u_char *ngx_cpystrn(u_char *dst, u_char *src, size_t n);
//字符串賦值，且dst為NULL結尾
u_char *ngx_pstrdup(ngx_pool_t *pool, ngx_str_t *src);
//從pool內申請空間，並使用src賦值，不保證NULL結尾
字符串長度
#define ngx_strlen(s) strlen((const char *) s)
size_t ngx_strnlen(u_char *p, size_t n);
//返回第一個'\0'或者n
大小寫轉換
#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);
字符串比對
#define ngx_strncmp(s1, s2, n) strncmp((const char *) s1, (const char *) s2, n)
//調用前需要保證s1與s2長度一致
#define ngx_strcmp(s1, s2) strcmp((const char *) s1, (const char *) s2)
//s1與s2都需要NULL結尾
ngx_int_t ngx_rstrncmp(u_char *s1, u_char *s2, size_t n);
//調用前需要保證s1與s2長度一致，使用較少，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);
//忽略大小寫比對，s1需要NULL結尾，調用前需要保證s1與s2長度一致
ngx_int_t ngx_strncasecmp(u_char *s1, u_char *s2, size_t n);
//忽略大小寫比對，調用前需要保證s1與s2長度一致
ngx_int_t ngx_rstrncasecmp(u_char *s1, u_char *s2, size_t n);
//忽略大小寫比對，調用前需要保證s1與s2長度一致
ngx_int_t ngx_memn2cmp(u_char *s1, u_char *s2, size_t n1, size_t n2);
//內部判斷長度相等
ngx_int_t ngx_dns_strcmp(u_char *s1, u_char *s2);
//忽略大小寫比對，且忽略最后的'.'字符
ngx_int_t ngx_filename_cmp(u_char *s1, u_char *s2, size_t n);
//根據操作系統，選擇是否忽略大小寫，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默認NULL結尾
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結尾，n為s1長度
u_char *ngx_strstrn(u_char *s1, char *s2, size_t n);
//在s1中搜索子串s2，s1需要NULL結尾，n為s2長度-1
u_char *ngx_strcasestrn(u_char *s1, char *s2, size_t n);
//忽略大小寫，在s1中搜索子串s2，s1需要NULL結尾，n為s2長度-1
u_char *ngx_strlcasestrn(u_char *s1, u_char *last, u_char *s2, size_t n);
//忽略大小寫，在[s1,last]中搜索子串s2，n為s2長度-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，外部保證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的內部函數，用於不定長參數的函數使用
字符串/數字轉換
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);
字符串編解碼
#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);