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Add a function for packing bits into a byte buffer. This will be needed when encoding the audio data in ALAC format.

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git-svn-id: file:///home/lennart/svn/public/pulseaudio/branches/coling@2368 fefdeb5f-60dc-0310-8127-8f9354f1896f
This commit is contained in:
Colin Guthrie 2008-05-06 00:28:04 +00:00
parent 66cf1d1f66
commit 8fb58e3a90
1 changed files with 52 additions and 0 deletions
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52
src/modules/rtp/raop_client.c
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@ -92,6 +92,58 @@ struct pa_raop_client {
void* userdata;
};
/**
* Function to write bits into a buffer.
* @param buffer Handle to the buffer. It will be incremented if new data requires it.
* @param bit_pos A pointer to a position buffer to keep track the current write location (0 for MSB, 7 for LSB)
* @param size A pointer to the byte size currently written. This allows the calling function to do simple buffer overflow checks
* @param data The data to write
* @param data_bit_len The number of bits from data to write
*/
static inline void bit_writer(uint8_t **buffer, uint8_t *bit_pos, int *size, uint8_t data, uint8_t data_bit_len) {
int bits_left, bit_overflow;
uint8_t bit_data;
if (!data_bit_len)
return;
/* If bit pos is zero, we will definatly use at least one bit from the current byte so size increments. */
if (!*bit_pos)
*size = 1;
/* Calc the number of bits left in the current byte of buffer */
bits_left = 7 - *bit_pos + 1;
/* Calc the overflow of bits in relation to how much space we have left... */
bit_overflow = bits_left - data_bit_len;
if (bit_overflow >= 0) {
/* We can fit the new data in our current byte */
/* As we write from MSB->LSB we need to left shift by the overflow amount */
bit_data = data << bit_overflow;
if (*bit_pos)
**buffer |= bit_data;
else
**buffer = bit_data;
/* If our data fits exactly into the current byte, we need to increment our pointer */
if (0 == bit_overflow) {
/* Do not increment size as it will be incremeneted on next call as bit_pos is zero */
*buffer += 1;
*bit_pos = 0;
} else {
*bit_pos += data_bit_len;
}
} else {
/* bit_overflow is negative, there for we will need a new byte from our buffer */
/* Firstly fill up what's left in the current byte */
bit_data = data >> -bit_overflow;
**buffer |= bit_data;
/* Increment our buffer pointer and size counter*/
*buffer += 1;
*size += 1;
**buffer = data << (8 + bit_overflow);
*bit_pos = -bit_overflow;
}
}
static int rsa_encrypt(uint8_t *text, int len, uint8_t *res) {
char n[] =
"59dE8qLieItsH1WgjrcFRKj6eUWqi+bGLOX1HL3U3GhC/j0Qg90u3sG/1CUtwC"