General helper tools for signatures that use base64 encodings. More...
#include <utilities/sigutils.h>
Static Public Member Functions | |
| static constexpr unsigned | decodeSingle (char c) |
| Determine the integer value represented by the given base64 character. More... | |
| static constexpr char | encodeSingle (unsigned c) |
| Determine the base64 character that represents the given integer value. More... | |
| static constexpr bool | isValid (char c) |
| Is the given character a valid base64 character? More... | |
| template<typename IntType > | |
| static void | encodeInt (std::string &s, IntType val, unsigned nChars) |
| Append a base64 encoding of the given integer to the given string. More... | |
| template<typename IntType > | |
| static IntType | decodeInt (const char *s, unsigned nChars) |
| Read the integer that is encoded at the beginning of the given base64 string. More... | |
| template<typename InputIterator > | |
| static char | encodeTrits (InputIterator trits, unsigned nTrits) |
| Returns a single base64 character that encodes up to three trits, given using an input iterator. More... | |
| template<int nTrits> | |
| static constexpr char | encodeTrits (const std::array< uint8_t, nTrits > &trits) |
| Returns a single base64 character that encodes up to three trits, given using a fixed-size array. More... | |
| template<typename OutputIterator > | |
| static void | decodeTrits (char c, OutputIterator result) |
| Decodes a single base64 character into three trits, and returns these using an output iterator. More... | |
| static constexpr std::array< uint8_t, 3 > | decodeTrits (char c) |
| Decodes a single base64 character into three trits, and returns these as a fixed-size array. More... | |
Detailed Description
General helper tools for signatures that use base64 encodings.
These are (in particular) used in the default encodings for Regina's own isomorphism signatures and knot signatures.
This base64 encoding uses the characters: a..zA..Z0..9+-
- Warning
- Note that this base64 encoding uses a different set of printable symbols from the encoding used in utilities/base64.h. This should not be a problem: Regina uses this encoding exclusively for signatures, and uses utilities/base64.h exclusively for encoding files.
Member Function Documentation
◆ decodeInt()
|
inlinestatic |
Read the integer that is encoded at the beginning of the given base64 string.
It will be assumed that the integer is encoded using nChars base64 characters, each containing 6 bits of the integer, with the lowest-significance bits encoded in the first characters.
The inverse to this routine is encodeInt().
- Precondition
- The given string contains at least nChars characters.
- Python
- The template argument IntType is taken to be a native C++
long.
- Template Parameters
-
IntType a native C++ integer type, such as uint8_t, orunsigned, orlong long. The result will be assembled using bitwise OR and bitwise shift lefts, and it is assumed that the programmer has chosen an integer type large enough to contain whatever values they expect to read.
- Parameters
-
s the string from which the encoded base64 characters should be read. nChars the number of base64 characters to read.
- Returns
- the native integer that was encoded.
◆ decodeSingle()
|
inlinestaticconstexpr |
Determine the integer value represented by the given base64 character.
The inverse to this routine is encodeSingle().
- Parameters
-
c a base64 character, which must be one of the 64 printable characters described in the class notes.
- Returns
- the corresponding integer, which will be between 0 and 63 inclusive.
◆ decodeTrits() [1/2]
|
inlinestaticconstexpr |
Decodes a single base64 character into three trits, and returns these as a fixed-size array.
A trit is either 0, 1 or 2.
The inverse to this routine is encodeTrits(); see that routine for details of the encoding.
- Parameters
-
c the base64 character to decode.
- Returns
- an array containing the three trits that had been encoded in the given base64 character.
◆ decodeTrits() [2/2]
|
inlinestatic |
Decodes a single base64 character into three trits, and returns these using an output iterator.
A trit is either 0, 1 or 2.
The inverse to this routine is encodeTrits(); see that routine for details of the encoding.
- Python
- Not present; instead you can use the variant of this routine that takes one argument and returns a fixed-size array.
- Parameters
-
c the base64 character to decode. result an output iterator pointing to the location where the resulting trits will be stored; it must be possible to write and advance this iterator at least three times. Each trit will be written as a uint8_t.
◆ encodeInt()
|
inlinestatic |
Append a base64 encoding of the given integer to the given string.
The integer will be broken into nChars distinct 6-bit blocks, and the lowest-significance blocks will be written first.
The inverse to this routine is decodeInt().
- Precondition
- The given integer val is non-negative, and fits within 6nChars bits.
- Python
- The template argument IntType is taken to be a native C++
long.
- Template Parameters
-
IntType a native C++ integer type, such as uint8_t, orunsigned, orlong long.
- Parameters
-
s the string that resulting characters should be appended to. val the integer to encode. nChars the number of base64 characters to use.
◆ encodeSingle()
|
inlinestaticconstexpr |
Determine the base64 character that represents the given integer value.
The inverse to this routine is decodeSingle().
- Parameters
-
c an integer between 0 and 63 inclusive.
- Returns
- the corresponding printable base64 character.
◆ encodeTrits() [1/2]
|
inlinestaticconstexpr |
Returns a single base64 character that encodes up to three trits, given using a fixed-size array.
A trit is either 0, 1 or 2.
The given trits will be packed into a single base64 character, with the first trit representing the lowest-significance bits of the underlying integer and so on.
The inverse to this routine is decodeTrits().
- Template Parameters
-
mTrits the number of trits to encode; this must be between 0 and 3 inclusive.
- Parameters
-
trits the array of trits to encode. Each trit must take the value 0, 1 or 2.
- Returns
- the resulting printable base64 character.
◆ encodeTrits() [2/2]
|
inlinestatic |
Returns a single base64 character that encodes up to three trits, given using an input iterator.
A trit is either 0, 1 or 2.
The given trits will be packed into a single base64 character, with the first trit representing the lowest-significance bits of the underlying integer and so on.
The inverse to this routine is decodeTrits().
- Python
- Not present; instead you can use the variant of this routine that takes the trits as a fixed-size array.
- Parameters
-
trits an input iterator pointing to the first trit to encode; it must be possible to read and advance this iterator at least nTrits times. Each trit will be cast to a uint8_t, and must take the value 0, 1 or 2.nTrits the number of trits to encode; this must be at most 3.
- Returns
- the resulting printable base64 character.
◆ isValid()
|
inlinestaticconstexpr |
Is the given character a valid base64 character?
- Returns
trueif and only if the given character is one of the 64 printable characters described in the class notes.
The documentation for this struct was generated from the following file:
- utilities/sigutils.h