improve bitstream read efficiency

Signed-off-by: Siebren Weertman <siebren.weertman@heliox-energy.com>

Author: Siebren Weertman

src/input/code_templates/c/static_code/exi_bitstream.c.jinja

@@ -172,7 +172,7 @@ int exi_bitstream_write_bits(exi_bitstream_t* stream, size_t bit_count, uint32_t
     }
 
     const size_t remaining_bits = 8 - stream->bit_count;
-    if (remaining_bits > bit_count) {
+    if (remaining_bits >= bit_count) {
         stream->data[stream->byte_pos] |= (uint8_t)((value << (remaining_bits - bit_count)));
         stream->bit_count += bit_count;
         if (stream->bit_count == 8) {
@@ -228,16 +228,33 @@ int exi_bitstream_read_bits(exi_bitstream_t* stream, size_t bit_count, uint32_t*
 
     int error = EXI_ERROR__NO_ERROR;
 
-    for (size_t n = 0; n < bit_count; n++)
-    {
-        uint8_t bit;
-        error = exi_bitstream_read_bit(stream, &bit);
-        if (error != EXI_ERROR__NO_ERROR)
-        {
-            break;
+    error = exi_bitstream_has_overflow(stream);
+    if (error != 0) {
+        return error;
+    }
+
+    const size_t remaining_bits = 8 - stream->bit_count;
+    if (remaining_bits >= bit_count) {
+        *value = (uint32_t)((stream->data[stream->byte_pos] >> (remaining_bits - bit_count)) & ((1 << bit_count) - 1));
+        stream->bit_count += bit_count;
+    } else {
+        *value = (uint32_t)(stream->data[stream->byte_pos] & ((1 << remaining_bits) - 1));
+        bit_count = (bit_count - remaining_bits);
+        stream->bit_count = 8;
+        error = exi_bitstream_has_overflow(stream);
+
+        while (bit_count >= 8) {
+            *value = (*value << 8) | stream->data[stream->byte_pos];
+            bit_count -= 8;
+            if (stream->byte_pos < stream->data_size) {
+                stream->byte_pos++;
+            } else {
+                error = EXI_ERROR__BITSTREAM_OVERFLOW;
+            }
         }
 
-        *value = (*value << 1u) | bit;
+        *value = (*value << bit_count) | (stream->data[stream->byte_pos] >> (8 - bit_count));
+        stream->bit_count = bit_count;
     }
 {%- if add_debug_code == 1 %}