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Add histogram fields in header file that allow specifying edges.

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This commit is contained in:
George Kadianakis 2019-02-13 16:58:15 +02:00
parent c320c52e89
commit f07c6ae57c
1 changed files with 46 additions and 11 deletions
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57
src/core/or/circuitpadding.h
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@ -228,13 +228,15 @@ typedef uint16_t circpad_statenum_t;
#define CIRCPAD_STATENUM_MAX (UINT16_MAX)
/** A histogram is used to sample padding delays given a machine state. This
* constant defines the maximum histogram width (i.e. the max number of bins)
* constant defines the maximum histogram width (i.e. the max number of bins).
*
* Each histogram bin is twice as large as the previous. Two exceptions: The
* first bin has zero width (which means that minimum delay is applied to the
* next padding cell), and the last bin (infinity bin) has infinite width
* (which means that the next padding cell will be delayed infinitely). */
#define CIRCPAD_MAX_HISTOGRAM_LEN (sizeof(circpad_delay_t)*8 + 1)
* The current limit is arbitrary and could be raised if there is a need,
* however too many bins will be hard to serialize in the future.
*
* Memory concerns are not so great here since the corresponding histogram and
* histogram_edges arrays are global and not per-circuit.
*/
#define CIRCPAD_MAX_HISTOGRAM_LEN (100)
/**
* A state of a padding state machine. The information here are immutable and
@ -248,15 +250,48 @@ typedef uint16_t circpad_statenum_t;
* or the consensus.
*/
typedef struct circpad_state_t {
/** If a histogram is used for this state, this specifies the number of bins
* of this histogram. Histograms must have at least 2 bins.
/**
* If a histogram is used for this state, this specifies the number of bins
* of this histogram. Histograms must have at least 2 bins.
*
* If a delay probability distribution is used for this state, this is set
* to 0. */
* In particular, the following histogram:
*
* Tokens
* +
* 10 | +----+
* 9 | | | +---------+
* 8 | | | | |
* 7 | | | +-----+ |
* 6 +----+ Bin+-----+ | +---------------+
* 5 | | #1 | | | | |
* | Bin| | Bin | Bin | Bin #4 | Bin #5 |
* | #0 | | #2 | #3 | | (infinity bin)|
* | | | | | | |
* | | | | | | |
* 0 +----+----+-----+-----+---------+---------------+
* 0 100 200 350 500 1000 ∞ microseconds
*
* would be specified the following way:
* histogram_len = 6;
* histogram[] = { 6, 10, 6, 7, 9, 6 }
* histogram_edges[] = { 0, 100, 200, 350, 500, 1000 }
*
* If a delay probability distribution is used for this state, this is set
* to 0. */
circpad_hist_index_t histogram_len;
/** The histogram itself: an array of uint16s of tokens, whose
* widths are exponentially spaced, in microseconds */
* widths are exponentially spaced, in microseconds.
*
* This array must have histogram_len elements. */
circpad_hist_token_t histogram[CIRCPAD_MAX_HISTOGRAM_LEN];
/* The histogram bin edges in usec.
*
* Each element of this array specifies the left edge of the corresponding
* bin. The rightmost edge is always infinity and is not specified in this
* array.
*
* This array must have histogram_len+1 elements. */
circpad_delay_t histogram_edges[CIRCPAD_MAX_HISTOGRAM_LEN+1];
/** Total number of tokens in this histogram. This is a constant and is *not*
* decremented every time we spend a token. It's used for initializing and
* refilling the histogram. */