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authorColin Guthrie <pulse@colin.guthr.ie>2008-05-06 00:28:04 +0000
committerColin Guthrie <pulse@colin.guthr.ie>2008-10-08 20:32:07 +0100
commit8fb58e3a9082bafc3aa7b874d2bba9258b29cb38 (patch)
tree0227f82861736a94a79c32c64e9f4667d25c7c1d /src/modules/rtp
parent66cf1d1f66c90b5f92d67a00ea2c1f6404453d97 (diff)
Add a function for packing bits into a byte buffer. This will be needed when encoding the audio data in ALAC format.
git-svn-id: file:///home/lennart/svn/public/pulseaudio/branches/coling@2368 fefdeb5f-60dc-0310-8127-8f9354f1896f
Diffstat (limited to 'src/modules/rtp')
-rw-r--r--src/modules/rtp/raop_client.c52
1 files changed, 52 insertions, 0 deletions
diff --git a/src/modules/rtp/raop_client.c b/src/modules/rtp/raop_client.c
index 18e596b0..fbcbe4bb 100644
--- a/src/modules/rtp/raop_client.c
+++ b/src/modules/rtp/raop_client.c
@@ -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"