Prettify HCB decoding

Insipiered by #192. We do not actually need out-of bounds checks, because Huffman tables are pretty well defined and proven to be "self-contained", i.e. no input bit sequence can escape the table.
knik0 · Dec 11, 2023 · cb9a92d · cb9a92d
1 parent 216f00e
commit cb9a92d
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Showing 14 changed files with 1,217 additions and 1,187 deletions.
diff --git a/libfaad/codebook/hcb.h b/libfaad/codebook/hcb.h
@@ -78,6 +78,9 @@ extern "C" {
 #define INTENSITY_HCB2 14
 #define INTENSITY_HCB  15
 
+/* Maximal accessed codebook index. */
+#define LAST_CB_IDX    11
+
 /* 1st step table */
 typedef struct
 {
@@ -115,16 +118,6 @@ typedef struct
     int8_t data[2];
 } hcb_bin_pair;
 
-hcb *hcb_table[];
-hcb_2_quad *hcb_2_quad_table[];
-hcb_2_pair *hcb_2_pair_table[];
-hcb_bin_pair *hcb_bin_table[];
-uint8_t hcbN[];
-uint8_t unsigned_cb[];
-int hcb_2_quad_table_size[];
-int hcb_2_pair_table_size[];
-int hcb_bin_table_size[];
-
 #include "codebook/hcb_1.h"
 #include "codebook/hcb_2.h"
 #include "codebook/hcb_3.h"
@@ -138,7 +131,6 @@ int hcb_bin_table_size[];
 #include "codebook/hcb_11.h"
 #include "codebook/hcb_sf.h"
 
-
 #ifdef __cplusplus
 }
 #endif

diff --git a/libfaad/codebook/hcb_1.h b/libfaad/codebook/hcb_1.h
@@ -36,7 +36,8 @@
  *
  * Used to find offset into 2nd step table and number of extra bits to get
  */
-static hcb hcb1_1[] = {
+static hcb hcb1_1[32] = {
+    /* 1 bit codeword */
     { /* 00000 */ 0, 0 },
     { /*       */ 0, 0 },
     { /*       */ 0, 0 },
@@ -53,6 +54,8 @@ static hcb hcb1_1[] = {
     { /*       */ 0, 0 },
     { /*       */ 0, 0 },
     { /*       */ 0, 0 },
+
+    /* 5 bit codewords */
     { /* 10000 */ 1, 0 },
     { /* 10001 */ 2, 0 },
     { /* 10010 */ 3, 0 },
@@ -75,13 +78,15 @@ static hcb hcb1_1[] = {
 
     /* 9/10/11 bit codewords */
     { /* 11111 */ 49, 6 }
+
+    /* Size of second level table is 49 + 64 = 113 */
 };
 
 /* 2nd step table
  *
  * Gives size of codeword and actual data (x,y,v,w)
  */
-static hcb_2_quad hcb1_2[] = {
+static hcb_2_quad hcb1_2[113] = {
     /* 1 bit codeword */
     { 1,  0,  0,  0,  0 },
 

diff --git a/libfaad/codebook/hcb_10.h b/libfaad/codebook/hcb_10.h
@@ -36,7 +36,7 @@
  *
  * Used to find offset into 2nd step table and number of extra bits to get
  */
-static hcb hcb10_1[] = {
+static hcb hcb10_1[64] = {
     /* 4 bit codewords */
     { /* 000000 */ 0, 0 },
     { /*        */ 0, 0 },
@@ -112,13 +112,15 @@ static hcb hcb10_1[] = {
     { /* 111110 */ 129, 4 },
     /* 10/11/12 bit codewords */
     { /* 111111 */ 145, 6 }
+
+    /* Size of second level table is 145 + 64 = 209 */
 };
 
 /* 2nd step table
  *
  * Gives size of codeword and actual data (x,y,v,w)
  */
-static hcb_2_pair hcb10_2[] = {
+static hcb_2_pair hcb10_2[209] = {
     /* 4 bit codewords */
     { 4,  1,  1 },
     { 4,  1,  2 },

diff --git a/libfaad/codebook/hcb_11.h b/libfaad/codebook/hcb_11.h
@@ -36,7 +36,7 @@
  *
  * Used to find offset into 2nd step table and number of extra bits to get
  */
-static hcb hcb11_1[] = {
+static hcb hcb11_1[32] = {
     /* 4 bits */
     { /* 00000 */ 0, 0 },
     { /*       */ 0, 0 },
@@ -92,13 +92,15 @@ static hcb hcb11_1[] = {
 
     /* 10/11/12 bits */
     { /* 11111 */ 246, 7 }
+
+     /* Size of second level table is 246 + 128 = 374 */
 };
 
 /* 2nd step table
  *
  * Gives size of codeword and actual data (x,y,v,w)
  */
-static hcb_2_pair hcb11_2[] = {
+static hcb_2_pair hcb11_2[374] = {
     /* 4 */
     { 4,  0,  0 },
     { 4,  1,  1 },

diff --git a/libfaad/codebook/hcb_2.h b/libfaad/codebook/hcb_2.h
@@ -36,13 +36,18 @@
  *
  * Used to find offset into 2nd step table and number of extra bits to get
  */
-static hcb hcb2_1[] = {
+static hcb hcb2_1[32] = {
+    /* 3 bit codeword */
     { /* 00000 */ 0, 0 },
     { /*       */ 0, 0 },
     { /*       */ 0, 0 },
-    { /*       */ 0, 0 },
+    { /* 00011 */ 0, 0 },
+
+    /* 4 bit codeword */
     { /* 00100 */ 1, 0 },
-    { /*       */ 1, 0 },
+    { /* 00101 */ 1, 0 },
+
+    /* 5 bit codewords */
     { /* 00110 */ 2, 0 },
     { /* 00111 */ 3, 0 },
     { /* 01000 */ 4, 0 },
@@ -79,13 +84,15 @@ static hcb hcb2_1[] = {
 
     /* 8/9 bit codewords */
     { /* 11111 */ 69, 4 }
+
+    /* Size of second level table is 69 + 16 = 85 */
 };
 
 /* 2nd step table
  *
  * Gives size of codeword and actual data (x,y,v,w)
  */
-static hcb_2_quad hcb2_2[] = {
+static hcb_2_quad hcb2_2[85] = {
     /* 3 bit codeword */
     { 3,  0,  0,  0,  0 },