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Source for wiki BlobAPI version 6

author

cowan

comment

ipnr

198.185.18.207

name

BlobAPI

readonly

text

This is a proposal for a WG2 bytevector API.  The conceit is that everything is a separate procedure with minimal arguments; this makes for a lot of procedures, but each one can be easily inlined by even a very dumb compiler, providing high efficiency.



=== Numeric procedures ===

 (`bytevector-<type><endian>-ref` ''bytevector n''`)`::
  Returns a Scheme number corresponding to the binary value encoded according to ''type'' beginning at offset ''n'' in ''bytevector''.
 (`bytevector-<type><endian>-set!` ''bytevector n v''`)`::
  Converts ''v'' to a binary value encoded according to ''type'' and places it into ''bytevector'' beginning at offset ''n''.

The types are:

 `u8`::
  unsigned 8-bit integer
 `s8`::
  signed 8-bit integer
 `u16`::
  unsigned 16-bit integer
 `s16`::
  signed 16-bit integer
 `u32`::
  unsigned 32-bit integer
 `s32`::
  signed 32-bit integer
 `u64`::
  unsigned 64-bit integer
 `s64`::
  signed 64-bit integer
 `u128`::
  unsigned 128-bit integer
 `s128`::
  signed 128-bit integer
 `f32`::
  32-bit IEEE float
 `fn32`::
  32-bit native float (may not be IEEE)
 `f64`::
  64-bit IEEE float in native endianism
 `fn64`::
  64-bit native float (may not be IEEE)
 `c64`::
  64-bit complex number (two 32-bit IEEE floats)
 `cn64`::
  64-bit complex number (two 32-bit native floats, may not be IEEE)
 `c128`::
  128-bit complex number (two 64-bit IEEE floats)
 `cn128`::
  128-bit complex number (two 64-bit native floats, may not be IEEE)

The endianism values are:

 (empty)::
  Native endianism (system-dependent)
 `le`::
  Little-endianism
 `be`::
  Big-endianism

Endianism is not applicable to the following types: `s8 u8 fn32 fn64 cn64 cn128`


=== String procedures ===

 (`bytevector-<encoding>-ref` ''bytevector n l''`)`::
  Returns a Scheme string corresponding to the binary value encoded according to ''encoding'' beginning at offset ''n'' in ''bytevector'' and continuing for ''l'' bytes.
 (`bytevector-<encoding>-set!` ''blob n v''`)`::
  Converts ''v'' to a binary string encoded according to ''encoding'' and places it into ''bytevector'' beginning at offset ''n''.  Returns the number of bytes encoded.

The encodings are:

 `utf8`::
  UTF-8 encoding
 `utf16`::
  UTF-16 encoding (respects BOM if present, defaults to native encoding otherwise)
 `utf16be`::
  UTF-16BE encoding (treats BOM as a normal character)
 `utf16le`::
  UTF-16LE encoding (treats BOM as a normal character)

=== Map, for-each, fold, unfold ===

'''TBD'''

=== Issues ===

Pick one:

  1. Offsets are in bytes and can be arbitrary
  1. Offsets are in bytes but must be naturally aligned (divisible by n for an n-byte value)
  1. Offsets are in n-byte units (forces natural alignment, SRFI-4 style)

Should `bytevector=?` be provided?

I've trashed the UTF-32 conversions because nobody uses UTF-32.  They can come back if somebody needs them.

time

2011-09-20 00:35:50