Changeset 5413 for SigProc/trunk/SigProc/utility.cpp

Timestamp:

10/14/07 14:02:19 (6 years ago)

Author:

jgaeddert

Message:

adding byte packing/unpacking functions to SigProc?

Files:

• SigProc/trunk/SigProc/utility.cpp (modified) (1 diff)

SigProc/trunk/SigProc/utility.cpp

@@ -163 +163 @@
 }
 
+//-----------------------------------------------------------------------------
+//
+// Bitwise functions
+//
+//-----------------------------------------------------------------------------
+
+/** \brief packs octets with one bit of information into a byte
+
+ */
+void pack_bytes(
+    char * input,
+    unsigned int input_length,
+    char * output,
+    unsigned int output_length,
+    unsigned int * num_written)
+{
+    div_t d = div(input_length,8);
+    unsigned int req_output_length = d.quot;
+    req_output_length += ( d.rem > 0 ) ? 1 : 0;
+    if ( output_length < req_output_length ) {
+        perror("ERROR: sigprocc_pack_bytes: output too short\n");
+        return;
+    }
+
+    unsigned int i;
+    unsigned int N = 0;         // number of bytes written to output
+    char byte = 0;
+
+    for (i=0; i<input_length; i++) {
+        byte |= input[i] & 0x01;
+
+        if ( (i+1)%8 == 0 ) {
+            output[N++] = byte;
+            byte = 0;
+        } else {
+            byte <<= 1;
+        }
+    }
+
+    if ( i%8 != 0 )
+        output[N++] = byte >> 1;
+
+    *num_written = N;
+}
+
+
+
+void unpack_bytes(
+    char * input,
+    unsigned int input_length,
+    char * output,
+    unsigned int output_length,
+    unsigned int * num_written)
+{
+    unsigned int i;
+    unsigned int N = 0;
+    char byte;
+
+    if ( output_length < 8*input_length ) {
+        perror("ERROR: sigprocc_unpack_bytes: output too short\n");
+        return;
+    }
+
+    for (i=0; i<input_length; i++) {
+        byte = input[i];
+        output[N++] = (byte >> 7) & 0x01;
+        output[N++] = (byte >> 6) & 0x01;
+        output[N++] = (byte >> 5) & 0x01;
+        output[N++] = (byte >> 4) & 0x01;
+        output[N++] = (byte >> 3) & 0x01;
+        output[N++] = (byte >> 2) & 0x01;
+        output[N++] = (byte >> 1) & 0x01;
+        output[N++] =  byte       & 0x01;
+    }
+
+    *num_written = N;
+}
+
+void repack_bytes(
+    char * input,
+    unsigned int input_sym_size,
+    unsigned int input_length,
+    char * output,
+    unsigned int output_sym_size,
+    unsigned int output_length,
+    unsigned int * num_written)
+{
+    div_t d = div(input_length*input_sym_size,output_sym_size);
+    unsigned int req_output_length = d.quot;
+    req_output_length += ( d.rem > 0 ) ? 1 : 0;
+    if ( output_length < req_output_length ) {
+        perror("ERROR: sigprocc_repack_bytes: output too short\n");
+        return;
+    }
+
+    unsigned int i;
+    char sym_in = 0;
+    char sym_out = 0;
+
+    // there is probably a more efficient way to do this, but...
+    unsigned int total_bits = input_length*input_sym_size;
+    unsigned int i_in = 0;  // input index
+    unsigned int i_out = 0; // output index
+    unsigned int k=0;       // input symbol enable
+    unsigned int n=0;       // output symbol enable
+    unsigned int v;         // bit mask
+
+    for (i=0; i<total_bits; i++) {
+        sym_out <<= 1;
+
+        // push input if necessary
+        if ( k == 0 )
+            sym_in = input[i_in++];
+
+        v = input_sym_size - k - 1;
+        sym_out |= (sym_in >> v) & 0x01;
+
+        // push output if available
+        if ( n == output_sym_size-1 ) {
+            output[i_out++] = sym_out;
+            sym_out = 0;
+        }
+
+        k = (k+1) % input_sym_size;
+        n = (n+1) % output_sym_size;
+    }
+
+    *num_written = i_out;
+}
+