C/C++实现segy文件的读取详解

  
//调用需要的C头文件
#include<stdio.h>   //C Language header file  
#include<stdlib.h>
#include<string.h>
#include<math.h>

//调用需要的C++头文件
#include<iostream>  // C++ header file
#include<vector>
#include<algorithm>

//调用非标准库
#include"alloc.h"   // 用于创建多维数组
#include"segy.h"   // 包含segy与bhed结构体，用于提取卷头和道头中采集、存储的信息

// 定义全局变量及命名空间
#define PI 3.141592654   //Constant Number Definition
#define EPS 0.0000001

using namespace std;

unsigned short exchangeLowHigh16(unsigned short Data_temp);//16位高低位转换函数  short占2字节，2*8
unsigned int exchangeLowHigh32(unsigned int Data_temp); //32位高低位转换函数  4*8
float ibm2pc(unsigned int Data_temp);      //IBM转PC数据
unsigned int pc2ibm(float input);          //PC转IBM数据
float ieee2pc(unsigned int Data_temp);   //IEEE转为PC

void trace_ibm2pc(float *data_output, int *data_input, int nt); //地震道数据由IBM转换为PC格式
void trace_pc2ibm(float *data_input, int *data_output, int nt); //地震道数据由PC转换为IBM格式

bool copySeismicDataIBM(const char *filenameInput, const char *filenameOutput); //Copy seismic data from Inputfile to Outputfile

//(1)调用需要的C头文件
#include<stdio.h>   // C Language header file  
#include<stdlib.h>
#include<string.h>
#include<math.h>

//(2)调用需要的C++头文件
#include<iostream>  // C++ header file
#include<vector>
#include<algorithm>

//(3)调用需要的非标准库头文件
#include"alloc.h"   // project header file 
#include"segy.h"
#include

//(4)定义全局常量
#define PI 3.141592654   // Constant Number Definition
#define EPS 0.0000001

//(5)声明命名空间
using namespace std;

//(6)声明函数名、输入、输出及其类型
unsigned short exchangeLowHigh16(unsigned short Data_temp);//16位高低位转换函数  short占2字节，2*8
unsigned int exchangeLowHigh32(unsigned int Data_temp); //32位高低位转换函数  4*8
float ibm2pc(unsigned int Data_temp);      //IBM转PC数据
unsigned int pc2ibm(float input);          //PC转IBM数据
float ieee2pc(unsigned int Data_temp);   //IEEE转为PC

void trace_ibm2pc(float *data_output, int *data_input, int nt); //地震道数据由IBM转换为PC格式
void trace_pc2ibm(float *data_input, int *data_output, int nt); //地震道数据由PC转换为IBM格式

bool copySeismicDataIBM(const char *filenameInput, const char *filenameOutput); //Copy seismic data from Inputfile to Outputfile

#include "ReadSeismic.h"
bool copySeismicDataIBM(const char *filenameInput, const char *filenameOutput){

    //实现代码        
    ...

}

bhed fileheader;        // file header  卷头
segy traceheader;       // trace header  道头
unsigned int nt=0;        // number of sample  采样点数
unsigned int sizefileheader=sizeof(fileheader);   // size of fileheader;
unsigned int sizetraceheader=sizeof(traceheader);  // size of traceheader;

unsigned int ncdp = 0;      // number of cdp  道数
long long  size_file = 0;   //size of input file
long long  size_trace = 0;  //size of per-trace

FILE *fpinput = NULL;   // input file pointer
FILE *fpoutput = NULL;   // output file pointer
float *dataInput = NULL;  // input data pointer
segy *traceheaderArray = NULL; // traceheader pointer
int* temp = NULL;  // temp pointer 

fpinput = fopen(filenameInput, "rb");  //open input file pointer 
fpoutput = fopen(filenameOutput,"wb");  //open output file pointer

//读写操作
...
    
//fopen()与fclose()成对出现，在对文件的操作完成后切记关闭文件
fclose(fpinput);  //close input file pointer
fclose(fpoutput); //close output file pointer

if(fpinput==NULL){                                            //如果文件指针为NULL
	printf("Cannot open %s file\n", filenameInput);           //打印“文件打开失败”
	return false;                                             //结束程序
}

if(fpoutput==NULL){
	printf("Cannot open %s file\n", filenameOutput);
	return false;
}

fread(&fileheader,sizefileheader,1,fpinput); // 从输入流(fpinput)中读取卷头信息到指定地址---->fileheader

nt = exchangeLowHigh16(fileheader.hns) // 高低位转换

_fseeki64(fpinput,0,SEEK_END);   // 从文件末尾偏移这个结构体0个长度给文件指针fpinput，即fpinput此时指向文件尾

size_file = _ftelli64(fpinput);  // 返回当前文件位置，即文件总字节数
size_trace = nt*sizeof(float)+sizetraceheader;  // 每一道的字节数 = 采样点字节数+道头字节数

ncdp = (size_file - (long long)sizefileheader)/size_trace; // 道数 = （文件总字节数 - 卷头字节数）/每一道的字节数

_fseeki64(fpinput,sizefileheader,SEEK_SET); // 从文件开头偏移sizefileheader（卷头字节数）个长度给指针fpinput，即fpinput此时指向第一道的开始
fwrite(&fileheader, sizefileheader, 1, fpoutput); // 先写入卷头

dataInput=alloc2float(nt,ncdp); // 分配nt*ncdp（采样点数×道数）所需的内存空间，用来存放二维地震道数据
//其中，alloc2float是卸载alloc.h中的函数，创建一个float型的二维数组
//dataInput为二级指针，可简记为dataInput指向每一行的开头

memset(dataInput[0], 0, nt*ncdp * sizeof(float)); // 从第一行的开头开始，将内存块中nt*ncdp个字符赋值为0
// dataInput指向每行开头，而dataInput[0]则为整个二维数组的起始位置

// 在内存的动态存储区中分配ncdp个长度为sizetraceheader的连续空间
traceheaderArray = (segy*)calloc(ncdp,sizetraceheader);

temp = (int*)calloc(nt,sizeof(int));

//逐道读取道头与地震道数据
for(int itrace = 0; itrace < ncdp; itrace++){
    fread(&traceheaderArray[itrace],sizetraceheader,1,fpinput); // &traceheaderArray[itrace]为第itrace道的地址，读取该道头信息
    fread(temp,nt * sizeof(float),1,fpinput); // 读取nt个采样点的信息并将结果指向temp
    
    // 使用trace_ibm2pc将temp位置后nt个采样点的数据，进行IBM-->PC的转换，结果指向每一道开头(dataInput[itrace])
    trace_ibm2pc(dataInput[itrace], temp, nt); 
    
}//end for(int itrace = 0; itrace < ncdp; itrace++)

//逐道写入道头与地震道数据
for (int itrace = 0; itrace < ncdp; itrace++) {
    fwrite(&traceheaderArray[itrace], sizetraceheader, 1, fpoutput); // 写入该道头信息
    
    // 使用trace_pc2ibm将temp位置后nt个采样点的数据，进行PC-->IBM的转换，结果指向每一道开头(dataInput[itrace])
    trace_pc2ibm(dataInput[itrace],temp,nt); 
    
    fwrite(temp, nt * sizeof(int), 1, fpoutput); // 以IBM的格式存回fpoutput
}//end for(int itrace = 0; itrace < ncdp; itrace++)
 // 在每个循环末尾的"}"添加备注，便于寻找和区分

//在写操作完成后释放内存
free(temp); // free temp pointer
free(traceheaderArray); // free traceheader pointer
free2float(dataInput);  // free data input pointer

#include "ReadSeismic.h"

bool copySeismicDataIBM(const char *filenameInput, const char *filenameOutput){

	segy traceheader;       // trace header 
	bhed fileheader;        // file header
	unsigned int nt = 0;        // number of sample
	unsigned int sizetraceheader = sizeof(traceheader);  // size of traceheader;
	unsigned int sizefileheader = sizeof(fileheader);   // size of fileheader;
	unsigned int ncdp = 0;     // number of cdp
	long long   size_file = 0;  //size of input file
	long long  size_trace = 0;  //size of per-trace

	FILE *fpinput = NULL;   // input file pointer
	FILE *fpoutput = NULL;   //output file pointer
	float **dataInput = NULL;  //input data pointer
	segy *traceheaderArray = NULL; //
	int* temp = NULL;

	fpinput = fopen(filenameInput, "rb");  //open input file pointer 
	fpoutput = fopen(filenameOutput, "wb");  //open output file pointer


	if (fpinput == NULL) {
		printf("Cannot open %s file\n", filenameInput);
		return false;
	}

	if (fpoutput == NULL) {
		printf("Cannot open %s file\n", filenameOutput);
		return false;
	}

	fread(&fileheader, sizefileheader, 1, fpinput);

	nt = fileheader.hns;
	nt = exchangeLowHigh16(fileheader.hns);
	_fseeki64(fpinput, 0, SEEK_END);
	size_file = _ftelli64(fpinput);
	size_trace = nt * sizeof(float) + sizetraceheader;

	ncdp = (size_file - (long long)sizefileheader) / size_trace;

	_fseeki64(fpinput, sizefileheader, SEEK_SET);


	dataInput = alloc2float(nt, ncdp);
	memset(dataInput[0], 0, nt*ncdp * sizeof(float));
	traceheaderArray = (segy*)calloc(ncdp, sizetraceheader);

	temp = (int*)calloc(nt,sizeof(int));


	fwrite(&fileheader,sizefileheader,1, fpoutput);
	for (int itrace = 0; itrace < ncdp; itrace++) {

		fread(&traceheaderArray[itrace], sizetraceheader, 1, fpinput);
		fread(temp, nt * sizeof(int), 1, fpinput);
		trace_ibm2pc(dataInput[itrace], temp, nt);
	}//end for(int itrace = 0; itrace < ncdp; itrace++)

	for (int itrace = 0; itrace < ncdp; itrace++) {
		fwrite(&traceheaderArray[itrace], sizetraceheader, 1, fpoutput);
		trace_pc2ibm(dataInput[itrace],temp,nt);
		fwrite(temp, nt * sizeof(int), 1, fpoutput);
	}//end for(int itrace = 0; itrace < ncdp; itrace++)


	free(temp);
	free(traceheaderArray);
	free2float(dataInput);  // free data input pointer
	fclose(fpoutput); //close output file pointer
	fclose(fpinput);  //close input file pointer
	return true;
}

#include"ReadSeismic.h"

void main(){

	copySeismicDataIBM("Azi6-Ang35-BZ19-6-1.segy","Outputibm.segy");

}