Improve escape sequences support in *printf(...)

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Source

• src/usr/lib/stdio.c

Specification

Source: https://en.wikipedia.org/wiki/Printf_format_string#Format_placeholder_specification

• syntax for a format placeholder: %[parameter][flags][width][.precision][length]type

To keep things simple we can go with the subset of the following options to build an minimum viable product

• Type field:
  • [ ] '%'
  • [ ] 'd' 'i'
  • [ ] 'u'
  • [ ] 'f' 'F'
  • [ ] ~'g' 'G'~
  • [ ] 'x' 'X'
  • [ ] 'o'
  • [ ] 's'
  • [ ] 'c'
  • [ ] 'p'
• Length field:
  • [ ] The field may be omitted (default, current behaviour)
  • [ ] 'l': 4 bytes same as 'not-specified'
  • [ ] 'll': 8 bytes
  • [ ] ~'L': 96 bits? or bits?~
    • https://en.wikipedia.org/wiki/Long_double#Implementations
    • https://godbolt.org/z/EME3zdcjG => 12 bytes == 96 bits
  • [ ] 'z': 4 bytes same as 'not-specified'
  • Flags field:
  • [ ] The field may be omitted (default, current behaviour)
  • [ ] '-' minus
  • [ ] '+' plus
  • [ ] ' ' space
  • [ ] '0'
  • Width field:
  • [ ] The field may be omitted (default, current behaviour)
  • [ ] or a numeric integer value
  • [ ] or a dynamic value when passed as another argument when indicated by an asterisk *.
  • Precision field:
  • [ ] The field may be omitted (default, current behaviour)
  • [ ] or a numeric integer value
  • [ ] or a dynamic value when passed as another argument when indicated by an asterisk *.

Multiple small pull requests are way better than one giant one :)

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Length field sub tasks are blocked on #32