Implement calculation of L, P, and P1

Cargo.toml

@@ -6,10 +6,10 @@ version = "0.0.0"
 authors = ["Christopher Berner <christopherberner@gmail.com>"]
 
 [dependencies]
+primal = "0.2"
 
 [dev-dependencies]
 criterion = "0.2"
-primal = "0.2"
 rand = "0.6"
 
 [[bench]]

src/encoder.rs

@@ -1,6 +1,7 @@
 use base::EncodingPacket;
 use PayloadId;
 use systematic_constants::extended_source_block_symbols;
+use systematic_constants::num_pi_symbols;
 
 pub struct SourceBlockEncoder {
     source_block_id: u8,
@@ -29,6 +30,7 @@ impl SourceBlockEncoder {
         for i in 0..((extended_source_symbols - self.num_source_symbols())*self.symbol_size as u32) {
             extended_data.push(0);
         }
+
     }
 
     pub fn all_source_packets(&self) -> Vec<EncodingPacket> {

src/systematic_constants.rs

@@ -541,6 +541,34 @@ pub fn num_lt_symbols(source_block_symbols: u32) -> u32 {
     panic!(); // unreachable
 }
 
+// Calculates, L, the number of intermediate symbols, for a given number of source block symbols
+// See section 5.3.3.3
+pub fn num_intermediate_symbols(source_block_symbols: u32) -> u32 {
+    extended_source_block_symbols(source_block_symbols) +
+        num_ldpc_symbols(source_block_symbols) +
+        num_hdpc_symbols(source_block_symbols)
+}
+
+// Calculates, P, the number of PI symbols, for a given number of source block symbols
+// See section 5.3.3.3
+pub fn num_pi_symbols(source_block_symbols: u32) -> u32 {
+    num_intermediate_symbols(source_block_symbols) - num_lt_symbols(source_block_symbols)
+}
+
+// Calculates P1, smallest prime greater than P. See 5.3.3.3
+pub fn calculate_p1(source_block_symbols: u32) -> u32 {
+    let mut p1 = num_pi_symbols(source_block_symbols);
+    while !primal::is_prime(p1 as u64) {
+        if p1 % 2 == 0 {
+            p1 += 1;
+        }
+        else {
+            p1 += 2;
+        }
+    }
+    p1
+}
+
 #[cfg(test)]
 mod tests {
     use systematic_constants::MAX_SOURCE_SYMBOLS_PER_BLOCK;