我正在读取大小为 4096 的数组寄存器中的文件。
我在循环之外有一个容器数组,我想按顺序将数据块“附加”到它,最快和最有效的方法是什么?
PointRecord4 * AllRegisters = new PointRecord4[ptr->Number_of_Point_records];
if (ptr->Point_Data_Format_ID == 4)
switch ((*ptr).Point_Data_Format_ID)
{
case 4:
{
PointRecord4 registers[4096];
ULONG32 pointsToRead = 4096;
ULONG32 pointsLoaded = 0;
ULONG32 i;
for (i = 0; pointsLoaded < ptr->Number_of_Point_records; i += pointsToRead)
{
pointsToRead = std::min(pointsToRead, ptr->Number_of_Point_records - pointsLoaded);
input_file.read(PTR(®isters), sizeof(PointRecord4) * pointsToRead);
pointsLoaded += pointsToRead;
//Insert registers[4096] into AllRegisters, Appending it
}
} break;
}
我试图简单地迭代 4096 并推回向量,但这非常慢。
以下是我的完整代码:
#include "vgl.h"
#include <fstream>
#include <iostream>
#include <vector>
#include <string.h>
using namespace std;
#define PTR reinterpret_cast<char *>
#pragma pack(1)
typedef struct LasHeader
{
char File_Signature[4]; // 4 Bytes
UINT16 FileSourceID; // 2 Bytes
UINT16 Global_Encoding; // 2 Bytes
ULONG32 GUID1; // 4 Bytes
UINT16 GUID2; // 2 Bytes
UINT16 GUID3; // 2 Bytes
UCHAR GUID4[8]; // 2 Bytes
UCHAR Version_Major; // 1 Bytes
UCHAR Version_Minor; // 1 Bytes
CHAR System_Identifier[32]; // 32 Bytes
CHAR Generating_Software[32]; // 32 Bytes
UINT16 File_Creation_Day_Of_Year; // 2 Bytes
UINT16 File_Creation_Year; // 2 Bytes
UINT16 Header_Size; // 2 Bytes
ULONG32 Offset_to_point_data; // 4 Bytes
ULONG32 Number_of_Variable_Length_Records; // 4 Bytes
CHAR Point_Data_Format_ID; // 1 Bytes
UINT16 Point_Data_Record_Length; // 2 Bytes
ULONG32 Number_of_Point_records; // 4 Bytes
ULONG32 Number_of_points_by_return[5]; // 20 Bytes / Verified
double X_Scale_Factor; // 8 bytes / Verified
double Y_Scale_Factor; // 8 bytes
double Z_Scale_Factor; // 8 bytes
double X_Offset; // 8 bytes
double Y_Offset; // 8 bytes
double Z_Offset; // 8 bytes
double Max_X; // 8 bytes
double Min_X; // 8 bytes
double Max_Y; // 8 bytes
double Min_Y; // 8 bytes
double Max_Z; // 8 bytes
double Min_Z; // 8 bytes
#ifdef FULLWAVE
unsigned long long Start_of_Waveform_Data_Packet_Record; // 8 bytes
#endif
union
{
char* MemoryBlock;
};
} *header;
struct PointRecord4
{
UINT32 X;
UINT32 Y;
UINT32 Z;
UINT16 Intensity;
CHAR BitMask;
CHAR Classification;
CHAR ScanAngleRank;
CHAR UserData;
UINT16 PointSourceID;
double GPSTime;
CHAR WPDI;
UINT64 WFOffset;
UINT32 WFPacketSize;
float WFReturnLocation;
float WFXt;
float WFYt;
float WFZt;
};
extern header ptr = new LasHeader;
HRESULT OpenLasFile(char *path)
{
HRESULT result;
ifstream input_file(path, ios::in | ios::binary);
result = GetLastError();
input_file.read(PTR(ptr), sizeof(LasHeader));
result = GetLastError();
input_file.seekg (ptr->Offset_to_point_data, input_file.beg);
PointRecord4 * AllRegisters = new PointRecord4[ptr->Number_of_Point_records];
if (ptr->Point_Data_Format_ID == 4)
switch ((*ptr).Point_Data_Format_ID)
{
case 4:
{
PointRecord4 registers[4096];
ULONG32 pointsToRead = 4096;
ULONG32 pointsLoaded = 0;
ULONG32 i;
for (i = 0; pointsLoaded < ptr->Number_of_Point_records; i += pointsToRead)
{
pointsToRead = std::min(pointsToRead, ptr->Number_of_Point_records - pointsLoaded);
input_file.read(PTR(®isters), sizeof(PointRecord4) * pointsToRead);
pointsLoaded += pointsToRead;
//Insert registers[4096] into AllRegisters, Appending it
}
} break;
}
input_file.close();
return result;
}