D:/work/code_by/CbmrEngine/SongItem.cpp

查看本檔案說明文件.

/*==============================================================================
TSongItem代表的是一首資料庫中的歌，其欄位包括所有在index檔中的資料，還有db檔中的
資料。
《注意》目前對於複歌的處理還不夠完整，例如複製和寫入時並沒有考慮到複歌的部份
==============================================================================*/
#include <math.h>
#include <string.h>
#include <stdlib.h>
#include "SongItem.h"

/*==============================================================================
功能：建構子
==============================================================================*/
TSongItem::TSongItem()
{
  start = 0;
  note = NULL;
  mid = NULL;
  noteIndex = NULL;
  refrainIndex = NULL;
  midRefrainIndex = NULL;
  noteSize = midSize = noteIndexSize = refrainIndexSize = 0;
  score = 0.0;
  Fields = new TMyStringList();
}

/*==============================================================================
功能：解構子
==============================================================================*/
TSongItem::~TSongItem()
{
  delete[] note;
  FreeMid();
  FreeRefrain();
  delete Fields;
}

/*==============================================================================
功能：設定
傳入：line為index檔中的一行字串
==============================================================================*/
void TSongItem::SetProperty(char *line)
{//Q:注意refStr有五個地方要改!
 // char *token, *value, refStr[100];
  char *token, *value, *refStr;//第一個
  int ref[100], len;

  if (line == NULL)
    return;

  //refStr[0] = '\0';
refStr = NULL;//第二個
  len = strlen(line);
  if (line[len - 1] == '\n')
    line[len - 1] = '\0';
  //將index檔中的一行字串拆成一個個token
  token = strtok(line, "\t");
  while (token)
  {
    if ((value = strchr(token, '=')) != NULL)  //沒有"="則不視為欄位
    {
      value++;
      if (*value != '\0' && *value != ' ')  //若"xxx="後面沒有字串或是等於空白則當做沒有此欄位
      {
        if (!strncmp(token, "start=", 6))
          start = atoi(value);
        else if (!strncmp(token, "size=", 5))
          noteSize = atoi(value);
        else if (!strncmp(token, "refrain=", 8))
        {
//          strncpy(refStr, value, 99);
                          delete[] refStr;
                  refStr = new char[strlen(value) + 1];
          strcpy(refStr, value);//以上三行為第三個

                }
        else
        //Q:加的是xxx=xxx為一個token
          Fields->Add(token);
      }
    }
    token = strtok(NULL, "\t");
  }
//  if (refStr[0] != '\0')  //有標示複歌
  if (refStr != NULL)  //有標示複歌//第四個
  {
    token = strtok(refStr, "+");

    while (token)
    {
    //Q:refrainIndex裡面長這個音符在note的哪裡.
    //Q:比方第一個複歌index是10,則refrainIndex[0]=20就是note[10*2]的地方.乘2的理由如下  
      ref[refrainIndexSize++] = atoi(token) * 2;  //複歌位置，乘以2是要把第幾個音符換算成note陣列的第幾個元素
      token = strtok(NULL, "+");
    }
    delete[] refStr;
    refrainIndex = new int[refrainIndexSize];
    memcpy(refrainIndex, ref, refrainIndexSize * sizeof(int));  //複歌位置
  }
}

/*==============================================================================
功能：從db檔中讀取資料，放進note欄位
傳入：DbStream為db檔
      note中的時間單位是1/64秒，轉換後的單位是resampleRate/64秒
傳出：是否成功
==============================================================================*/
//Q:resampleRate=4
bool TSongItem::Read(TInputStream *DbStream, int resampleRate)
{
  unsigned char uc;
  delete[] note;
  note = new unsigned char[noteSize];
  DbStream->Reset();

  DbStream->Skip(start);
  DbStream->Reads(note, noteSize);
  uc = DbStream->Read();
  if (uc != 0xFF){
    return false;
}

  Ready(resampleRate);
  return true;
}

/*==============================================================================
功能：將一首歌寫進index和db檔
傳入：IndexStream為index檔，DbStream為db檔
==============================================================================*/
void TSongItem::Write(TOutputStream *IndexStream, TOutputStream *DbStream)
{
  char str[100];
  int i, j;
  unsigned char *encodedNote;

  start = DbStream->Size();
  sprintf(str, "start=%d\tsize=%d", start, noteSize);  //寫入index檔
  IndexStream->Writes(str, strlen(str));
  for (i = 0; i < Fields->count; i++)
  {
    sprintf(str, "\t%s", Fields->Strings(i));
    IndexStream->Writes(str, strlen(str));
  }
  if (refrainIndexSize > 0)
  {
    sprintf(str, "\trefrain=%d", refrainIndex[0]);
    IndexStream->Writes(str, strlen(str));
    for (i = 1; i < refrainIndexSize; i++)
    {
      sprintf(str, "+%d", refrainIndex[i]);
      IndexStream->Writes(str, strlen(str));
    }
  }
  IndexStream->Write('\n');
  DbStream->Writes(note, noteSize);  //寫入db檔
  DbStream->Write(0xFF);
}
/*==============================================================================
功能：將note轉換成中介格式
傳入：note中的時間單位是1/64秒，轉換後的單位是resampleRate/64秒
      scale是放大倍率
//Q: resampleRate = 4,scale=INTEGER_SCALE=10  //因為用整數代替浮點數而乘上的倍數        
==============================================================================*/
void TSongItem::NoteToMid(int resampleRate, int scale)
{
        
  int i, j, k, size;
//Q:mid和noteIndex都是這裡才建的.mid是中介格式,noteIndex每個音符起點在mid中的索引,
//Q:它紀錄了note和mid的對應.又原本的note可能有包含休止符.noteIndex是去掉休止符後和mid的對應

  delete[] mid;
  mid = new int[midSize];
  delete[] noteIndex;
//  printf("noteIndexSize is %d\n",noteIndexSize);      

  noteIndex = new int[noteIndexSize];
//  printf("BBB\n");    

  for (i = 0, j = -1, k = 0, size = 0; i < midSize; i++)
  {
 //Q:i是mid的index值,j是note的index值,k是noteIndex的index值
 //Q:j是音長,j-1是音高.同一個音很長的時候,前一次的size += note[j += 2]就會加很多,
 //Q:那種情況下while就不會進入,直到跑完那個音長為止,所以mid可以是mid[3]~mid[30]都是Do這樣.
 //Q:所以mid是note的展開,但又經過resample處理.ex:note裡是Do8mi4Do4(音高音長)轉成mid變成DoDomiDo
    while (size <= i * resampleRate)
    {
      size += note[j += 2];
      if (k < noteIndexSize && note[j - 1] != 0)
        noteIndex[k++] = i;  //每個音符起點在mid中的索引
        //Q:有點像原本的note對應到mid的哪一個值.noteIndex[1],noteIndex[2],noteIndex[3]可能都等於2,
        //Q:表示note的這三個音符都指向mid[2]=某個音高,不過這三個音符不一定都相等.被縮小了~減成1/4
    }
    //Q:將note對應的音高值存進mid;resampleRate是4,表示轉成中介格式只取1/4
    //Q:轉成中介格式有很多方法,如四點取中位數,這裡看起來是取四點的最後一點(以音長為基準,而不是音高)
    mid[i] = note[j - 1] * scale;
//printf("%d=%d,",i,mid[i]);

  }

}
/*==============================================================================
功能：將中介格式釋放掉，為了節省記憶體
==============================================================================*/
void TSongItem::FreeMid(void)
{
  delete[] mid;
  mid = NULL;
  delete[] noteIndex;
  noteIndex = NULL;
}
/*==============================================================================
功能：將複歌索引釋放掉
==============================================================================*/
void TSongItem::FreeRefrain(void)
{
  refrainIndexSize = 0;
  delete[] refrainIndex;
  refrainIndex = NULL;
  delete[] midRefrainIndex;
  midRefrainIndex = NULL;
}
/*==============================================================================
功能：當note遭修改時，必須呼叫此函式，否則無法哼唱搜尋
==============================================================================*/
void TSongItem::Ready(int resampleRate)
{//Q:resampleRate=4
  int i, j, k, size;

  //算出展開成中介格式後的長度
  //Q:db檔中每首歌是以音高音長音高音長!
  for (i = 1, midSize = 0; i < noteSize; i += 2)
    midSize += note[i];
  midSize /= resampleRate;
  //算出這首歌有幾個音符為起點的片段
  //Q:其實是在算有幾個音符片段,但是會扣掉後面一段SEGMENT_SIZE的樣子
  //Q:?????這段不懂.音符為起點?"資料庫歌曲的片段長度"SEGMENT_SIZE=128
  //Q:noteSize-1是減掉每首歌最後寫入的0xFF嗎?j是音高or音長?音長?
  //Q:但是這個for只跑一次,一旦if成立就break?那不是只有找一次128?
  //Q:照這樣看來,就是從後面往前,找到即將大於(128+1)*4的那個點
  for (j = noteSize - 1, size = 0; j >= 1; j -= 2)
    if ((size += note[j]) >= (SEGMENT_SIZE + 1) * resampleRate)
      break;
  //Q:下面這一行應該縮排?在上面的for之下?
  //Q:其實上面那個for只用來刪去最後的128*4???從上面break後size本來就會符合下面這個if
//  j = noteSize - 1;
  if (size >= (SEGMENT_SIZE + 1) * resampleRate)
    for (i = 0, noteIndexSize = 0; i < j; i += 2)
      if (note[i] != 0) //Q:看起來像去掉休止符,因為音高=0表示沒有音高
        noteIndexSize++;
  //找出這首歌每個複歌起點
  if (noteSize > 0)
  {
    delete[] midRefrainIndex;
    midRefrainIndex = new int[refrainIndexSize + 1];

    midRefrainIndex[0] = 0;  //一定從頭比對
    for (i = 0, j = -1, k = 0, size = 0; k < refrainIndexSize; i++)
      while (size <= i * resampleRate)
      {
        size += note[j += 2];
    //           printf("j is%d and noteSizeis %d\n",j,noteSize);

        if (refrainIndex[k] == j - 1)
        {
          midRefrainIndex[++k] = i;  //複歌位置在mid中的索引
          if (k >= refrainIndexSize)
            break;
        }
      }
  }
}

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