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/// @file
/// Embedded bencode support, header definitions.
// 2012-09-29 <>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
/// Encoder class to generate Bencode on the fly (no buffer storage needed).
class EmBencode {
EmBencode () {}
/// Push a string out in Bencode format.
/// @param str The zero-terminated string to send out (without trailing \0).
static void push (const char* str) {
push(str, strlen(str));
/// Push arbitrary bytes in Bencode format.
/// @param ptr Pointer to the data to send out.
/// @param len Number of data bytes to send out.
static void push (const void* ptr, uint8_t len) {
PushData(ptr, len);
/// Push a signed integer in Bencode format.
/// @param val The integer to send (this implementation supports 32 bits).
static void push (long val) {
if (val < 0) {
val = -val;
/// Start a new new list. Must be matched with a call to endList().
/// Entries can be nested with more calls to startList(), startDict(), etc.
static void startList () {
/// Terminate a list, started earlier with a call to startList().
static void endList () {
/// Start a new new dictionary. Must be matched with a call to endDict().
/// Dictionary entries must consist of a string key plus an arbitrary value.
/// Entries can be nested with more calls to startList(), startDict(), etc.
static void startDict () {
/// Terminate a dictionary, started earlier with a call to startDict().
static void endDict () {
static void PushCount (uint32_t num) {
char buf[11];
PushData(ultoa(num, buf, 10), strlen(buf));
static void PushEnd () {
static void PushData (const void* ptr, uint8_t len) {
for (const char* p = (const char*) ptr; len-- > 0; ++p)
/// This function is not implemented in the library. It must be supplied by
/// the caller to implement the actual writing of caharacters.
static void PushChar (char ch);
/// Decoder class, needs an external buffer to collect the incoming data.
class EmBdecode {
/// Types of tokens, as returned by nextToken().
enum { T_STRING = 0, T_NUMBER = 251, T_DICT, T_LIST, T_POP, T_END };
/// Initialize a decoder instance with the specified buffer space.
/// @param buf Pointer to the buffer which will be used by the decoder.
/// @param len Size of the buffer, must be in the range 50 to 255.
EmBdecode (char* buf, uint8_t len)
: bufPtr (buf), bufLen (len) { reset(); }
/// Reset the decoder - can be called to prepare for a new round of decoding.
uint8_t reset ();
/// Process a single incoming caharacter.
/// @return Returns a count > 0 when the buffer contains a complete packet.
uint8_t process (char ch);
/// Call this after process() is done, to extract each of the data tokens.
/// @returns Returns one of the T_STRING .. T_END enumeration codes.
uint8_t nextToken ();
/// Extract the last token as string (works for T_STRING and T_NUMBER).
/// @param plen This variable will receive the size, if present.
/// @return Returns pointer to a zero-terminated string in the decode buffer.
const char* asString (uint8_t* plen =0);
/// Extract the last token as number (also works for strings if numeric).
/// @return Returns the decoded integer, max 32-bit signed in this version.
long asNumber ();
void AddToBuf (char ch);
char level, *bufPtr;
uint8_t bufLen, count, next, last, state;
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