C语言 在 C 中进行查找表的最佳方法是什么？
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What's the best way to do a lookup table in C?
提问by PICyourBrain
I am working on an embedded C project. I have an LCD display and for each character there is a 5x7 dot matrix. To display a specific character you have to shift in 5 bytes that correlate with the dots to turn on. So I need to make some kind of look-up table with a key where I can pass in an ASCII character, and get an array of 5 bytes returned... For example, a call to this function like this,
我正在研究一个嵌入式 C 项目。我有一个 LCD 显示屏，每个字符都有一个 5x7 点阵。要显示特定字符，您必须移动与要打开的点相关的 5 个字节。所以我需要用一个键创建某种查找表，我可以在其中传入一个 ASCII 字符，并返回一个 5 个字节的数组......例如，像这样调用这个函数，
GetDisplayBytes('A');
GetDisplayBytes('A');
should return `an array like this...
应该返回一个像这样的数组......
C[0] = 0x7E : C[1] = 0x90 : C[2] = 0x90 : C[3] = 0x90 : C[4] = 0x7E
C[0] = 0x7E : C[1] = 0x90 : C[2] = 0x90 : C[3] = 0x90 : C[4] = 0x7E
What would be the best way to do this in C?
在 C 中执行此操作的最佳方法是什么？
回答by Carl Norum
I would make arrays for the contiguous ASCII blocks you want to use. data. Something like this:
我会为您要使用的连续 ASCII 块制作数组。数据。像这样的东西：
uint8_t displayBytesLetters[] =
{
0x73, 0x90, 0x90, 0x90, 0x73, // 'A'
.
.
.
};
uint8_t displayBytesDigits[] =
{
0x12, 0x15, 0x25, 0x58, 0x80, // '0'
.
.
.
};
Then your GetDisplayBytes()is something like:
然后你GetDisplayBytes()是这样的：
uint8_t *GetDisplayBytes(char c)
{
if (isdigit(c))
return &displayBytes[5*(c - '0')];
else if (isupper(c))
return &displayBytes[5*(c - 'A')];
else
return NULL;
}
Pass the returned pointer to whatever function outputs the data:
将返回的指针传递给任何输出数据的函数：
void DoDisplay(uint8_t *displayBytes)
{
int i;
for (i = 0; i < 5; i++)
{
SendOutput(displayBytes[i]);
}
}
回答by James Curran
typedef char LCDDATA[5];
LCDDATA lcdTable[256] = { {0,0,0,0,0}, // char 0
{.....}, // char 1
}
LCDDATA GetDisplayBytes(char chr)
{
return lcdTable[chr];
}
This is basically making an array of arrays.
这基本上是制作一个数组数组。
