Small refactoring to reduce code duplication.

diff --git a/turbopfor.h b/turbopfor.h
index 51ee66ea65bc8defe56ee2b53ad2799859db2f2a..d60fe29ca3edae1005de0dcfec5c1aa7be6293a5 100644 (file)
--- a/turbopfor.h
+++ b/turbopfor.h
@@ -208,6 +208,31 @@ const unsigned char *decode_for_interleaved(const unsigned char *in, Docid *out)
        return in + bytes_for_packed_bits(BlockSize, bit_width);
 }
 
+template<class Docid>
+const unsigned char *decode_pfor_bitmap_exceptions(const unsigned char *in, unsigned num, unsigned bit_width, Docid *out)
+{
+       const unsigned exception_bit_width = *in++;
+       const uint64_t *exception_bitmap_ptr = reinterpret_cast<const uint64_t *>(in);
+       in += div_round_up(num, 8);
+
+       int num_exceptions = 0;
+
+       BitReader bs(in, exception_bit_width);
+       for (unsigned i = 0; i < num; i += 64, ++exception_bitmap_ptr) {
+               uint64_t exceptions = read_le<uint64_t>(exception_bitmap_ptr);
+               if (num - i < 64) {
+                       // We've read some bytes past the end, so clear out the junk bits.
+                       exceptions &= (1ULL << (num - i)) - 1;
+               }
+               for (; exceptions != 0; exceptions &= exceptions - 1, ++num_exceptions) {
+                       unsigned idx = (ffsll(exceptions) - 1) + i;
+                       out[idx] = bs.read() << bit_width;
+               }
+       }
+       in += bytes_for_packed_bits(num_exceptions, exception_bit_width);
+       return in;
+}
+
 // PFor block with bitmap exceptions. Layout:
 //
 //  - Bit width (6 bits) | type << 6
@@ -221,29 +246,8 @@ const unsigned char *decode_pfor_bitmap(const unsigned char *in, unsigned num, D
        memset(out, 0, num * sizeof(Docid));
 
        const unsigned bit_width = *in++ & 0x3f;
-       const unsigned exception_bit_width = *in++;
-
-       // Decode exceptions.
-       {
-               const uint64_t *exception_bitmap_ptr = reinterpret_cast<const uint64_t *>(in);
-               in += div_round_up(num, 8);
-
-               int num_exceptions = 0;
 
-               BitReader bs(in, exception_bit_width);
-               for (unsigned i = 0; i < num; i += 64, ++exception_bitmap_ptr) {
-                       uint64_t exceptions = read_le<uint64_t>(exception_bitmap_ptr);
-                       if (num - i < 64) {
-                               // We've read some bytes past the end, so clear out the junk bits.
-                               exceptions &= (1ULL << (num - i)) - 1;
-                       }
-                       for (; exceptions != 0; exceptions &= exceptions - 1, ++num_exceptions) {
-                               unsigned idx = (ffsll(exceptions) - 1) + i;
-                               out[idx] = bs.read() << bit_width;
-                       }
-               }
-               in += bytes_for_packed_bits(num_exceptions, exception_bit_width);
-       }
+       in = decode_pfor_bitmap_exceptions(in, num, bit_width, out);
 
        // Decode the base values, and delta-decode.
        Docid prev_val = out[-1];
@@ -262,27 +266,10 @@ const unsigned char *decode_pfor_bitmap_interleaved(const unsigned char *in, Doc
        memset(out, 0, BlockSize * sizeof(Docid));
 
        const unsigned bit_width = *in++ & 0x3f;
-       const unsigned exception_bit_width = *in++;
-
-       // Decode exceptions.
-       {
-               const uint64_t *exception_bitmap_ptr = reinterpret_cast<const uint64_t *>(in);
-               in += div_round_up(BlockSize, 8);
 
-               int num_exceptions = 0;
+       in = decode_pfor_bitmap_exceptions(in, BlockSize, bit_width, out);
 
-               BitReader bs(in, exception_bit_width);
-               for (unsigned i = 0; i < BlockSize; i += 64, ++exception_bitmap_ptr) {
-                       uint64_t exceptions = read_le<uint64_t>(exception_bitmap_ptr);
-                       for (; exceptions != 0; exceptions &= exceptions - 1, ++num_exceptions) {
-                               unsigned idx = (ffsll(exceptions) - 1) + i;
-                               out[idx] = bs.read() << bit_width;
-                       }
-               }
-               in += bytes_for_packed_bits(num_exceptions, exception_bit_width);
-       }
-
-       // Decode the base values, and delta-decode.
+       // Decode the base values.
        InterleavedBitReader<4> bs0(in + 0 * sizeof(uint32_t), bit_width);
        InterleavedBitReader<4> bs1(in + 1 * sizeof(uint32_t), bit_width);
        InterleavedBitReader<4> bs2(in + 2 * sizeof(uint32_t), bit_width);
@@ -293,6 +280,8 @@ const unsigned char *decode_pfor_bitmap_interleaved(const unsigned char *in, Doc
                out[i * 4 + 2] |= bs2.read();
                out[i * 4 + 3] |= bs3.read();
        }
+
+       // Delta-decode.
        Docid prev_val = out[-1];
        for (unsigned i = 0; i < BlockSize; ++i) {
                out[i] = prev_val = out[i] + prev_val + 1;