Documented varint

This commit is contained in:
jebes 2014-09-11 10:14:05 -04:00
parent c085e9294f
commit a70bf86037
4 changed files with 82 additions and 42 deletions

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@ -99,7 +99,7 @@ namespace tools
static decoded_block_sizes instance; static decoded_block_sizes instance;
private: private:
std::vector<int> m_data; std::vector<int> m_data;p
}; };
decoded_block_sizes decoded_block_sizes::instance; decoded_block_sizes decoded_block_sizes::instance;

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@ -47,7 +47,7 @@ using namespace epee;
namespace tools namespace tools
{ {
std::function<void(void)> signal_handler::m_handler; std::function<void(void)> signal_handler::m_handler;
#ifdef WIN32 #ifdef WIN32
std::string get_windows_version_display_string() std::string get_windows_version_display_string()

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@ -136,8 +136,8 @@ namespace tools
/*! \breif calles m_handler */ /*! \breif calles m_handler */
static void handle_signal() static void handle_signal()
{ {
/* static std::mutex m_mutex; */ static std::mutex m_mutex;
/* std::unique_lock<std::mutex> lock(m_mutex); */ std::unique_lock<std::mutex> lock(m_mutex);
m_handler(); m_handler();
} }

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@ -35,54 +35,94 @@
#include <utility> #include <utility>
#include <sstream> #include <sstream>
#include <string> #include <string>
/*! \file varint.h
* \breif provides the implementation of varint's
*
* The representation of varints is rather odd. The first bit of each
* octet is significant, it represents wheter there is another part
* waiting to be read. For example 0x8002 would return 0x200, even
* though 0x02 does not have its msb set. The actual way they are read
* is as follows: Strip the msb of each byte, then from left to right,
* read in what remains, placing it in reverse, into the buffer. Thus,
* the following bit stream: 0xff02 would return 0x027f. 0xff turns
* into 0x7f, is placed on the beggining of the buffer, then 0x02 is
* unchanged, since its msb is not set, and placed at the end of the
* buffer.
*/
namespace tools { namespace tools {
template<typename OutputIt, typename T> /*! \breif Error codes for varint
typename std::enable_if<std::is_integral<T>::value && std::is_unsigned<T>::value, void>::type */
write_varint(OutputIt &&dest, T i) { enum {
while (i >= 0x80) { /* \breif Represents the overflow error */
*dest++ = (static_cast<char>(i) & 0x7f) | 0x80; EVARINT_OVERFLOW = -1,
i >>= 7; /* \breif Represents a non conical represnetation */
} EVARINT_REPRESENT = -2,
*dest++ = static_cast<char>(i); };
}
template<typename t_type> /*! \breif writes a varint to a stream.
std::string get_varint_data(const t_type& v) */
template<typename OutputIt, typename T>
/* Requires T to be both an integral type and unsigned, should be a compile error if it is not */
typename std::enable_if<std::is_integral<T>::value && std::is_unsigned<T>::value, void>::type
write_varint(OutputIt &&dest, T i) {
/* Make sure that there is one after this */
while (i >= 0x80) {
*dest = (static_cast<char>(i) & 0x7f) | 0x80;
++dest;
i >>= 7; /* I should be in multiples of 7, this should just get the next part */
}
/* writes the last one to dest */
*dest = static_cast<char>(i);
dest++; /* Seems kinda pointless... */
}
/*! \breif Returns the string that represents the varint
*/
template<typename T>
std::string get_varint_data(const T& v)
{ {
std::stringstream ss; std::stringstream ss;
write_varint(std::ostreambuf_iterator<char>(ss), v); write_varint(std::ostreambuf_iterator<char>(ss), v);
return ss.str(); return ss.str();
} }
/*! \breif reads in the varint as pointer to by InputIt into i
template<int bits, typename InputIt, typename T> */
template<int bits, typename InputIt, typename T>
typename std::enable_if<std::is_integral<T>::value && std::is_unsigned<T>::value && 0 <= bits && bits <= std::numeric_limits<T>::digits, int>::type typename std::enable_if<std::is_integral<T>::value && std::is_unsigned<T>::value && 0 <= bits && bits <= std::numeric_limits<T>::digits, int>::type
read_varint(InputIt &&first, InputIt &&last, T &i) { read_varint(InputIt &&first, InputIt &&last, T &write) {
int read = 0; int read = 0;
i = 0; write = 0;
for (int shift = 0;; shift += 7) { for (int shift = 0;; shift += 7) {
if (first == last) { if (first == last) {
return read; // End of input. return read;
} }
unsigned char byte = *first++; unsigned char byte = *first;
++read; ++first;
if (shift + 7 >= bits && byte >= 1 << (bits - shift)) { ++read;
return -1; // Overflow. if (shift + 7 >= bits && byte >= 1 << (bits - shift)) {
} return EVARINT_OVERFLOW;
if (byte == 0 && shift != 0) { }
return -2; // Non-canonical representation. if (byte == 0 && shift != 0) {
} return EVARINT_REPRESENT;
i |= static_cast<T>(byte & 0x7f) << shift; }
if ((byte & 0x80) == 0) {
break;
}
}
return read;
}
template<typename InputIt, typename T> write |= static_cast<T>(byte & 0x7f) << shift; /* Does the actualy placing into write, stripping the first bit */
int read_varint(InputIt &&first, InputIt &&last, T &i) {
return read_varint<std::numeric_limits<T>::digits, InputIt, T>(std::move(first), std::move(last), i); /* If there is no next */
if ((byte & 0x80) == 0) {
break;
}
} }
return read;
}
/*! \breif Wrapper around the other read_varint,
* Sets template parameters for you.
*/
template<typename InputIt, typename T>
int read_varint(InputIt &&first, InputIt &&last, T &i) {
return read_varint<std::numeric_limits<T>::digits, InputIt, T>(std::move(first), std::move(last), i);
}
} }