gccrs: libformat_parser: Add FFI safe interface

libgrust/ChangeLog:

	* libformat_parser/generic_format_parser/src/lib.rs: Add generic
	library.
	* libformat_parser/src/lib.rs: Add base for FFI interface.

libgrust/libformat_parser/src/lib.rs

@@ -5,8 +5,298 @@
 
 use std::ffi::CStr;
 
-// TODO: Use rustc's version here #3
-use generic_format_parser::Piece;
+mod ffi {
+    use std::ops::Deref;
+
+    // Note: copied from rustc_span
+    /// Range inside of a `Span` used for diagnostics when we only have access to relative positions.
+    #[derive(Copy, Clone, PartialEq, Eq, Debug)]
+    #[repr(C)]
+    pub struct InnerSpan {
+        pub start: usize,
+        pub end: usize,
+    }
+
+    // impl InnerSpan {
+    //     pub fn new(start: usize, end: usize) -> InnerSpan {
+    //         InnerSpan { start, end }
+    //     }
+    // }
+
+    /// The location and before/after width of a character whose width has changed from its source code
+    /// representation
+    #[derive(Copy, Clone, PartialEq, Eq)]
+    #[repr(C)]
+    pub struct InnerWidthMapping {
+        /// Index of the character in the source
+        pub position: usize,
+        /// The inner width in characters
+        pub before: usize,
+        /// The transformed width in characters
+        pub after: usize,
+    }
+
+    // impl InnerWidthMapping {
+    //     pub fn new(position: usize, before: usize, after: usize) -> InnerWidthMapping {
+    //         InnerWidthMapping {
+    //             position,
+    //             before,
+    //             after,
+    //         }
+    //     }
+    // }
+
+    /// Whether the input string is a literal. If yes, it contains the inner width mappings.
+    #[derive(Clone, PartialEq, Eq)]
+    #[repr(C)]
+    enum InputStringKind {
+        NotALiteral,
+        Literal {
+            width_mappings: Vec<InnerWidthMapping>,
+        },
+    }
+
+    /// The type of format string that we are parsing.
+    #[derive(Copy, Clone, Debug, Eq, PartialEq)]
+    #[repr(C)]
+    pub enum ParseMode {
+        /// A normal format string as per `format_args!`.
+        Format,
+        /// An inline assembly template string for `asm!`.
+        InlineAsm,
+    }
+
+    #[derive(Copy, Clone)]
+    #[repr(C)]
+    struct InnerOffset(usize);
+
+    /// A piece is a portion of the format string which represents the next part
+    /// to emit. These are emitted as a stream by the `Parser` class.
+    #[derive(Clone, Debug, PartialEq)]
+    #[repr(C)]
+    pub enum Piece<'a> {
+        /// A literal string which should directly be emitted
+        String(&'a str),
+        /// This describes that formatting should process the next argument (as
+        /// specified inside) for emission.
+        NextArgument(Box<Argument<'a>>),
+    }
+
+    /// Representation of an argument specification.
+    #[derive(Copy, Clone, Debug, PartialEq)]
+    #[repr(C)]
+    pub struct Argument<'a> {
+        /// Where to find this argument
+        pub position: Position<'a>,
+        /// The span of the position indicator. Includes any whitespace in implicit
+        /// positions (`{  }`).
+        pub position_span: InnerSpan,
+        /// How to format the argument
+        pub format: FormatSpec<'a>,
+    }
+
+    /// Specification for the formatting of an argument in the format string.
+    #[derive(Copy, Clone, Debug, PartialEq)]
+    #[repr(C)]
+    pub struct FormatSpec<'a> {
+        /// Optionally specified character to fill alignment with.
+        pub fill: Option<char>,
+        /// Span of the optionally specified fill character.
+        pub fill_span: Option<InnerSpan>,
+        /// Optionally specified alignment.
+        pub align: Alignment,
+        /// The `+` or `-` flag.
+        pub sign: Option<Sign>,
+        /// The `#` flag.
+        pub alternate: bool,
+        /// The `0` flag.
+        pub zero_pad: bool,
+        /// The `x` or `X` flag. (Only for `Debug`.)
+        pub debug_hex: Option<DebugHex>,
+        /// The integer precision to use.
+        pub precision: Count<'a>,
+        /// The span of the precision formatting flag (for diagnostics).
+        pub precision_span: Option<InnerSpan>,
+        /// The string width requested for the resulting format.
+        pub width: Count<'a>,
+        /// The span of the width formatting flag (for diagnostics).
+        pub width_span: Option<InnerSpan>,
+        /// The descriptor string representing the name of the format desired for
+        /// this argument, this can be empty or any number of characters, although
+        /// it is required to be one word.
+        pub ty: &'a str,
+        /// The span of the descriptor string (for diagnostics).
+        pub ty_span: Option<InnerSpan>,
+    }
+
+    /// Enum describing where an argument for a format can be located.
+    #[derive(Copy, Clone, Debug, PartialEq)]
+    #[repr(C)]
+    pub enum Position<'a> {
+        /// The argument is implied to be located at an index
+        ArgumentImplicitlyIs(usize),
+        /// The argument is located at a specific index given in the format,
+        ArgumentIs(usize),
+        /// The argument has a name.
+        ArgumentNamed(&'a str),
+    }
+
+    /// Enum of alignments which are supported.
+    #[derive(Copy, Clone, Debug, PartialEq)]
+    #[repr(C)]
+    pub enum Alignment {
+        /// The value will be aligned to the left.
+        AlignLeft,
+        /// The value will be aligned to the right.
+        AlignRight,
+        /// The value will be aligned in the center.
+        AlignCenter,
+        /// The value will take on a default alignment.
+        AlignUnknown,
+    }
+
+    /// Enum for the sign flags.
+    #[derive(Copy, Clone, Debug, PartialEq)]
+    #[repr(C)]
+    pub enum Sign {
+        /// The `+` flag.
+        Plus,
+        /// The `-` flag.
+        Minus,
+    }
+
+    /// Enum for the debug hex flags.
+    #[derive(Copy, Clone, Debug, PartialEq)]
+    #[repr(C)]
+    pub enum DebugHex {
+        /// The `x` flag in `{:x?}`.
+        Lower,
+        /// The `X` flag in `{:X?}`.
+        Upper,
+    }
+
+    /// A count is used for the precision and width parameters of an integer, and
+    /// can reference either an argument or a literal integer.
+    #[derive(Copy, Clone, Debug, PartialEq)]
+    #[repr(C)]
+    pub enum Count<'a> {
+        /// The count is specified explicitly.
+        CountIs(usize),
+        /// The count is specified by the argument with the given name.
+        CountIsName(&'a str, InnerSpan),
+        /// The count is specified by the argument at the given index.
+        CountIsParam(usize),
+        /// The count is specified by a star (like in `{:.*}`) that refers to the argument at the given index.
+        CountIsStar(usize),
+        /// The count is implied and cannot be explicitly specified.
+        CountImplied,
+    }
+
+    impl<'a> From<generic_format_parser::Piece<'a>> for Piece<'a> {
+        fn from(old: generic_format_parser::Piece<'a>) -> Self {
+            match old {
+                generic_format_parser::Piece::String(x) => Piece::String(x),
+                generic_format_parser::Piece::NextArgument(x) => {
+                    Piece::NextArgument(Box::new(Into::<Argument>::into(*x)))
+                }
+            }
+        }
+    }
+
+    impl<'a> From<generic_format_parser::Argument<'a>> for Argument<'a> {
+        fn from(old: generic_format_parser::Argument<'a>) -> Self {
+            Argument {
+                position: old.position.into(),
+                position_span: old.position_span.into(),
+                format: old.format.into(),
+            }
+        }
+    }
+
+    impl<'a> From<generic_format_parser::Position<'a>> for Position<'a> {
+        fn from(old: generic_format_parser::Position<'a>) -> Self {
+            match old {
+                generic_format_parser::Position::ArgumentImplicitlyIs(x) => {
+                    Position::ArgumentImplicitlyIs(x.into())
+                }
+                generic_format_parser::Position::ArgumentIs(x) => Position::ArgumentIs(x.into()),
+                generic_format_parser::Position::ArgumentNamed(x) => {
+                    Position::ArgumentNamed(x.into())
+                }
+            }
+        }
+    }
+
+    impl From<generic_format_parser::InnerSpan> for InnerSpan {
+        fn from(old: generic_format_parser::InnerSpan) -> Self {
+            InnerSpan {
+                start: old.start,
+                end: old.end,
+            }
+        }
+    }
+
+    impl<'a> From<generic_format_parser::FormatSpec<'a>> for FormatSpec<'a> {
+        fn from(old: generic_format_parser::FormatSpec<'a>) -> Self {
+            FormatSpec {
+                fill: old.fill,
+                fill_span: old.fill_span.map(Into::into),
+                align: old.align.into(),
+                sign: old.sign.map(Into::into),
+                alternate: old.alternate,
+                zero_pad: old.zero_pad,
+                debug_hex: old.debug_hex.map(Into::into),
+                precision: old.precision.into(),
+                precision_span: old.precision_span.map(Into::into),
+                width: old.width.into(),
+                width_span: old.width_span.map(Into::into),
+                ty: old.ty,
+                ty_span: old.ty_span.map(Into::into),
+            }
+        }
+    }
+
+    impl From<generic_format_parser::DebugHex> for DebugHex {
+        fn from(old: generic_format_parser::DebugHex) -> Self {
+            match old {
+                generic_format_parser::DebugHex::Lower => DebugHex::Lower,
+                generic_format_parser::DebugHex::Upper => DebugHex::Upper,
+            }
+        }
+    }
+
+    impl<'a> From<generic_format_parser::Count<'a>> for Count<'a> {
+        fn from(old: generic_format_parser::Count<'a>) -> Self {
+            match old {
+                generic_format_parser::Count::CountIs(x) => Count::CountIs(x),
+                generic_format_parser::Count::CountIsName(x, y) => Count::CountIsName(x, y.into()),
+                generic_format_parser::Count::CountIsParam(x) => Count::CountIsParam(x),
+                generic_format_parser::Count::CountIsStar(x) => Count::CountIsStar(x),
+                generic_format_parser::Count::CountImplied => Count::CountImplied,
+            }
+        }
+    }
+
+    impl From<generic_format_parser::Sign> for Sign {
+        fn from(old: generic_format_parser::Sign) -> Self {
+            match old {
+                generic_format_parser::Sign::Plus => Sign::Plus,
+                generic_format_parser::Sign::Minus => Sign::Minus,
+            }
+        }
+    }
+
+    impl From<generic_format_parser::Alignment> for Alignment {
+        fn from(old: generic_format_parser::Alignment) -> Self {
+            match old {
+                generic_format_parser::Alignment::AlignLeft => Alignment::AlignLeft,
+                generic_format_parser::Alignment::AlignRight => Alignment::AlignRight,
+                generic_format_parser::Alignment::AlignCenter => Alignment::AlignCenter,
+                generic_format_parser::Alignment::AlignUnknown => Alignment::AlignUnknown,
+            }
+        }
+    }
+}
 
 // FIXME: Rename?
 pub mod rust {
@@ -22,7 +312,7 @@ pub mod rust {
 
 #[repr(C)]
 pub struct PieceSlice {
-    base_ptr: *const Piece<'static /* FIXME: That's wrong */>,
+    base_ptr: *const ffi::Piece<'static /* FIXME: That's wrong */>,
     len: usize,
 }
 
@@ -32,7 +322,10 @@ pub extern "C" fn collect_pieces(input: *const libc::c_char) -> PieceSlice {
     let str = unsafe { CStr::from_ptr(input) };
 
     // FIXME: No unwrap
-    let pieces = rust::collect_pieces(str.to_str().unwrap());
+    let pieces: Vec<ffi::Piece<'_>> = rust::collect_pieces(str.to_str().unwrap())
+        .into_iter()
+        .map(Into::into)
+        .collect();
 
     PieceSlice {
         base_ptr: pieces.as_ptr(),