pht: rename and fix Pht::blobToString

A refactoring error led to blobToString outputing garbage. This patch fixes the
issue and enables output of a number of bits other than multiple of 8.

include/opendht/indexation/pht.h

@@ -239,7 +239,7 @@ ee     *
      * @throw out_of_range if bit is superior to blob size * 8
      */
     bool isActiveBit(const Blob &b, size_t pos) const {
-        if ( pos >= content_.size() * 8 )
+        if (pos >= content_.size() * 8)
             throw std::out_of_range("Can't detect active bit at pos, pos larger than prefix size or empty prefix");
 
         return ((b[pos / 8] >> (7 - (pos % 8)) ) & 1) == 1;
@@ -256,12 +256,14 @@ ee     *
      * @throw out_of_range if bit is superior to blob size * 8
      */
     void swapBit(Blob &b, size_t bit) {
-        if ( bit >= b.size() * 8 )
+        if (bit >= b.size() * 8)
             throw std::out_of_range("bit larger than prefix size.");
 
         size_t offset_bit = (8 - bit) % 8;
         b[bit / 8] ^= (1 << offset_bit);
     }
+
+    std::string firstBitsToString(const Blob&, size_t) const;
 };
 
 using Value = std::pair<InfoHash, dht::Value::Id>;

src/indexation/pht.cpp

@@ -25,26 +25,29 @@ namespace dht {
 namespace indexation {
 
 /**
- * Output the blob into string and readable way
+ * Get bit string representation of a blob for a specified length.
  *
- * @param bl   : Blob to print
+ * @param bl   A Blob
+ * @param len  The number of bits to consider.
  *
- * @return string that represent the blob into a readable way
+ * @return string that represent the blob
  */
-static std::string blobToString(const Blob &bl) {
+std::string Prefix::firstBitsToString(const Blob &bl, size_t len) const {
+    if (len >= bl.size() * 8)
+        throw std::out_of_range("specified length larger than blob size");
     std::stringstream ss;
-    auto bn = bl.size() % 8;
-    auto n = bl.size() / 8;
+    auto bn = len % 8;
 
-    for (size_t i = 0; i < bl.size(); i++)
-        ss << std::bitset<8>(bl[i]) << " ";
+    for (size_t i = 0; i < len/8; i++)
+        ss << std::bitset<8>(bl[i]);
     if (bn)
-        for (unsigned b=0; b < bn; b++)
-            ss << (char)((bl[n] & (1 << (7 - b))) ? '1':'0');
+        for (unsigned b = 0; b < bn; b++)
+            ss << (char)((bl[len/8] & (1 << (7 - b))) ? '1':'0');
 
     return ss.str();
 }
-std::string Prefix::toString() const { return blobToString(content_); }
+
+std::string Prefix::toString() const { return firstBitsToString(content_, size_); }
 
 void Pht::Cache::insert(const Prefix& p) {
     size_t i = 0;