go语言memset go语言适合做什么

memset()函数

1、memset是计算机中C/C++语言函数。将s所指向的某一块内存中的前n个 字节的内容全部设置为ch指定的ASCII值， 第二个值为指定的内存地址，块的大小由第三个参数指定，这个函数通常为新申请的内存做初始化工作， 其返回值为指向s的指针。

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函数介绍：void *memset(void *s, int ch, size_t n);

2、函数解释：将s中前n个字节 （typedef unsigned int size_t ）用 ch 替换并返回 s 。

memset：作用是在一段内存块中填充某个给定的值，它是对较大的结构体或数组进行清零操作的一种最快方法。

3、范例：

C语言操作yaml配置文件通用操作工具

在go语言中使用viper之类的库很方便的处理yaml配置文件，但是在c语言中就比较麻烦，经过一番思索和借助强大的github,发现了一个libyaml c库，但是网上的例子都比较麻烦，而且比较繁琐，就想法作了一个相对比较容易配置的解析应用，可以简单地类似viper 的模式进行配置实现不同的配置文件读取。如你的配置文件很复杂请按格式修改KeyValue 全局变量，欢迎大家一起完善

库请自行下载 GitHub - yaml/libyaml: Canonical source repository for LibYAML

直接上代码

yaml示例文件

%YAML 1.1

---

mqtt:

subtopic: "Control/#"

pubtopic: "bbt"

qos: 1

serveraddress: "tcp://192.168.0.25:1883"

clientid: "kvm_test"

writelog: false

writetodisk: false

outputfile: "./receivedMessages.txt"

hearttime: 30

#ifndef __CONFIG_H__

#define __CONFIG_H__

#ifdef __cplusplus

extern "C" {

#endif

/************************/

/* Minimum YAML version */

/************************/

#define YAML_VERSION_MAJOR 1

#define YAML_VERSION_MINOR 1

#define STRUCT_TYPE_NAME 100

#define INT_TYPE_NAME 101

#define STRING_TYPE_NAME 102

#define BOOL_TYPE_NAME 103

#define FLOAT_TYPE_NAME 104

#define MAP_TYPE_NAME 105

#define LIST_TYPE_NAME 106

typedef struct{

char *key;

void *value;

int valuetype;

char *parent;

}KeyValue,*pKeyValue;

#ifdef __cplusplus

}

#endif

#endif

#include

#include

#include

#include

#include

#include

#include

#include "config.h"

typedef struct {

char *SUBTOPIC; //string `yaml:"subtopic" mapstructure:"subtopic"` //"topic1"

char *PUBTOPIC; //string `yaml:"pubtopic" mapstructure:"pubtopic"`

int QOS; //byte `yaml:"qos" mapstructure:"qos"` //1

char *SERVERADDRESS; //string `yaml:"serveraddress" mapstructure:"serveraddress"` //= "tcp://mosquitto:1883"

char *CLIENTID; //string `yaml:"clientid" mapstructure:"clientid"` //= "mqtt_subscriber"

int HEARTTIME; //int `yaml:"hearttime" mapstructure:"hearttime"`

// CommandLocalPath string `yam:"commanlocalpath"`

}mqttSection,*pmqttSection;

typedef struct {

mqttSection Mqtt;// `yaml:"mqtt" mapstructure:"mqtt"`

// KVM kvmSection `yaml:"kvm" mapstructure:"kvm"`

}ConfigT;

ConfigT config;

static KeyValue webrtcconfig[]={

{"mqtt",config,STRUCT_TYPE_NAME,NULL},

{"subtopic",(config.Mqtt.SUBTOPIC),STRING_TYPE_NAME,"mqtt"},

{"pubtopic",(config.Mqtt.PUBTOPIC),STRING_TYPE_NAME,"mqtt"},

{"qos",(config.Mqtt.QOS),INT_TYPE_NAME,"mqtt"},

{"serveraddress",(config.Mqtt.SERVERADDRESS),STRING_TYPE_NAME,"mqtt"},

{"clientid",(config.Mqtt.CLIENTID),STRING_TYPE_NAME,"mqtt"},

{"hearttime",(config.Mqtt.HEARTTIME),INT_TYPE_NAME,"mqtt"},

{NULL,NULL,0,NULL},

};

int printConfig(ConfigT * pconfig){

if(pconfig==NULL) return -1;

printf("mqtt:r ");

if(pconfig-Mqtt.SUBTOPIC!=NULL) {printf("subtopic: %sr ",pconfig-Mqtt.SUBTOPIC); }

if(pconfig-Mqtt.SUBTOPIC!=NULL) {printf("pubtopic: %sr ",pconfig-Mqtt.PUBTOPIC); }

printf("qos: %dr ",config.Mqtt.QOS);

if(pconfig-Mqtt.SERVERADDRESS!=NULL) {printf("serveraddress: %sr ",pconfig-Mqtt.SERVERADDRESS); }

if(pconfig-Mqtt.CLIENTID!=NULL) {printf("clientid: %sr ",pconfig-Mqtt.CLIENTID); }

printf("hearttime: %dr ",config.Mqtt.HEARTTIME);

}

int freeConfig(ConfigT * pconfig){

if(pconfig==NULL) return -1;

if(pconfig-Mqtt.SERVERADDRESS!=NULL) {free(pconfig-Mqtt.SERVERADDRESS); }

if(pconfig-Mqtt.CLIENTID!=NULL) {free(pconfig-Mqtt.CLIENTID); }

if(pconfig-Mqtt.SUBTOPIC!=NULL) {free(pconfig-Mqtt.SUBTOPIC); }

}

char currentkey[100];

void getvalue(yaml_event_t event,pKeyValue *ppconfigs){

char *value = (char *)event.data.scalar.value;

pKeyValue pconfig=*ppconfigs;

char *pstringname;

while(pconfig-key!=NULL){

if(currentkey[0]!=0){

if(!strcmp(currentkey,pconfig-key))

{

switch(pconfig-valuetype){

case STRING_TYPE_NAME:

pstringname=strdup(value);

printf("get string value %sr ",pstringname);

*((char**)pconfig-value)=pstringname;

memset(currentkey, 0, sizeof(currentkey));

break;

case INT_TYPE_NAME:

*((int*)(pconfig-value))=atoi(value);

memset(currentkey, 0, sizeof(currentkey));

break;

case BOOL_TYPE_NAME:

if(!strcmp(value,"true")) *((bool*)(pconfig-value))=true;

else *((bool*)(pconfig-value))=false;

memset(currentkey, 0, sizeof(currentkey));

break;

case FLOAT_TYPE_NAME:

*((float*)(pconfig-value))=atof(value);

memset(currentkey, 0, sizeof(currentkey));

break;

case STRUCT_TYPE_NAME:

case MAP_TYPE_NAME:

case LIST_TYPE_NAME:

memset(currentkey, 0, sizeof(currentkey));

strncpy(currentkey,value,strlen(value));

break;

default:

break;

}

break;

}

//continue;

}else{

if(!strcmp(value,pconfig-key)){

strncpy(currentkey,pconfig-key,strlen(pconfig-key));

break;

}

}

pconfig++;

}

}

int Load_YAML_Config( char *yaml_file, KeyValue *(configs[]) )

{

struct stat filecheck;

yaml_parser_t parser;

yaml_event_t event;

bool done = 0;

unsigned char type = 0;

unsigned char sub_type = 0;

if (stat(yaml_file, filecheck) != false )

{

printf("[%s, line %d] Cannot open configuration file '%s'! %s", __FILE__, __LINE__, yaml_file, strerror(errno) );

return -1;

}

FILE *fh = fopen(yaml_file, "r");

if (!yaml_parser_initialize(parser))

{

printf("[%s, line %d] Failed to initialize the libyaml parser. Abort!", __FILE__, __LINE__);

return -1;

}

if (fh == NULL)

{

printf("[%s, line %d] Failed to open the configuration file '%s' Abort!", __FILE__, __LINE__, yaml_file);

return -1;

}

memset(currentkey, 0, sizeof(currentkey));

/* Set input file */

yaml_parser_set_input_file(parser, fh);

while(!done)

{

if (!yaml_parser_parse(parser, event))

{

/* Useful YAML vars: parser.context_mark.line+1, parser.context_mark.column+1, parser.problem, parser.problem_mark.line+1, parser.problem_mark.column+1 */

printf( "[%s, line %d] libyam parse error at line %ld in '%s'", __FILE__, __LINE__, parser.problem_mark.line+1, yaml_file);

}

if ( event.type == YAML_DOCUMENT_START_EVENT )

{

//yaml file first line is version

//%YAML 1.1

//---

yaml_version_directive_t *ver = event.data.document_start.version_directive;

if ( ver == NULL )

{

printf( "[%s, line %d] Invalid configuration file. Configuration must start with "%%YAML 1.1"", __FILE__, __LINE__);

}

int major = ver-major;

int minor = ver-minor;

if (! (major == YAML_VERSION_MAJOR minor == YAML_VERSION_MINOR) )

{

printf( "[%s, line %d] Configuration has a invalid YAML version. Must be 1.1 or above", __FILE__, __LINE__);

return -1;

}

}

else if ( event.type == YAML_STREAM_END_EVENT )

{

done = true;

}

else if ( event.type == YAML_MAPPING_END_EVENT )

{

sub_type = 0;

}

else if ( event.type == YAML_SCALAR_EVENT )

{

getvalue(event,configs);

}

}

return 0;

}

int main(int argc, char *argv[]){

pKeyValue pconfig=webrtcconfig[0];

Load_YAML_Config("../../etc/kvmagent.yml",pconfig);

printConfig(config);

freeConfig(config);

}

memset函数的用法？

在你申请了一块内存之后，

比如

int*p=null;

p=malloc(10*sizeof(int));//申请了10个int型内存

memset(p,0,10*sizeof(int));//全部初始化为0

memset的作用就是把你快连续的内存初始化为你给的值。

example

/*memset.c:thisprogramusesmemsetto

*setthefirstfourbytesofbufferto"*".

*/

#includememory.h

#includestdio.h

voidmain(void)

{

charbuffer[]="thisisatestofthememsetfunction";

printf("before:%s\n",buffer);

memset(buffer,'*',4);

printf("after:%s\n",buffer);

}

output

before:thisisatestofthememsetfunction

after:****isatestofthememsetfunction

memset(num,0,sizeof(num));什么意思

memset是个函数，百它在string.h头文件中有声明。它有三个参数，一度是所要set的首地址，二是set的值问，三是set的字节数。

string.h在c语言和c++语言中都被广泛的使用，但是具体情况不是很一样。由于传统的C++脱胎于C，所以传统C++中于C语言中对本词条的用法差不多，经过美国标准化组织修改标准化后的标准C++中，定义则是大不相同。

扩展资料：

程序例：

#includestdio.h #includestring.h int main(void) { char string[10]; char*str1="abcdefghi"; strcpy(string,str1); printf("%s\n",string); return 0; }