libpqxx
The C++ client library for PostgreSQL
 
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pqxx::string_traits< unsigned char > Struct Reference

You cannot convert an unsigned char to/from SQL. More...

+ Inheritance diagram for pqxx::string_traits< unsigned char >:

Static Public Member Functions

static zview to_buf (char *begin, char *end, unsigned char const &value)
 Return a string_view representing value, plus terminating zero.
 
static char * into_buf (char *begin, char *end, unsigned char const &value)
 Write value's string representation into buffer at begin.
 
static unsigned char from_string (std::string_view text)
 Parse a string representation of a TYPE value.
 
static std::size_t size_buffer (unsigned char const &value) noexcept
 Estimate how much buffer space is needed to represent value.
 
- Static Public Member Functions inherited from pqxx::forbidden_conversion< unsigned char >
static zview to_buf (char *, char *, unsigned char const &)
 
static char * into_buf (char *, char *, unsigned char const &)
 
static unsigned char from_string (std::string_view)
 
static std::size_t size_buffer (unsigned char const &) noexcept
 

Static Public Attributes

static constexpr bool converts_to_string
 Is conversion from TYPE to strings supported?
 
static constexpr bool converts_from_string
 Is conversion from string_view to TYPE supported?
 
- Static Public Attributes inherited from pqxx::forbidden_conversion< unsigned char >
static constexpr bool converts_to_string
 
static constexpr bool converts_from_string
 

Detailed Description

You cannot convert an unsigned char to/from SQL.

Converting this type may seem simple enough, but it's ambiguous: Did you mean the char value as a small integer? Or were you thinking of a single-character string (and if so, using what encoding)? Or perhaps it's just a raw byte value?

If you meant it as an integer, use an appropriate integral type such as int or short or unsigned int etc.

If you wanted a single-character string, use std::string_view (or a similar type such as std::string).

Or if you had a raw byte in mind, try pqxx::bytes_view instead.

Member Function Documentation

◆ from_string()

static unsigned char pqxx::string_traits< unsigned char >::from_string ( std::string_view text)
inlinestaticnodiscard

Parse a string representation of a TYPE value.

Throws conversion_error if value does not meet the expected format for a value of this type.

Warning
A null value has no string representation. Do not parse a null.

◆ size_buffer()

static std::size_t pqxx::string_traits< unsigned char >::size_buffer ( unsigned char const & value)
inlinestaticnodiscardnoexcept

Estimate how much buffer space is needed to represent value.

The estimate may be a little pessimistic, if it saves time.

The estimate includes the terminating zero.

◆ to_buf()

static zview pqxx::string_traits< unsigned char >::to_buf ( char * begin,
char * end,
unsigned char const & value )
inlinestaticnodiscard

Return a string_view representing value, plus terminating zero.

Produces a string_view containing the PostgreSQL string representation for value.

Warning
A null value has no string representation. Do not pass a null.

Uses the space from begin to end as a buffer, if needed. The returned string may lie somewhere in that buffer, or it may be a compile-time constant, or it may be null if value was a null value. Even if the string is stored in the buffer, its begin() may or may not be the same as begin.

The string_view is guaranteed to be valid as long as the buffer from begin to end remains accessible and unmodified.

Exceptions
pqxx::conversion_overrunif the provided buffer space may not be enough. For maximum performance, this is a conservative estimate. It may complain about a buffer which is actually large enough for your value, if an exact check gets too expensive.

Member Data Documentation

◆ converts_from_string

bool pqxx::string_traits< unsigned char >::converts_from_string
staticconstexpr

Is conversion from string_view to TYPE supported?

When defining your own conversions, specialise this as true to indicate that your string traits support from_string.

◆ converts_to_string

bool pqxx::string_traits< unsigned char >::converts_to_string
staticconstexpr

Is conversion from TYPE to strings supported?

When defining your own conversions, specialise this as true to indicate that your string traits support the conversions to strings.


The documentation for this struct was generated from the following file: