//! Functions and data from the RPI Bootrom.

/// A bootrom function table code.
pub type RomFnTableCode = [u8; 2];

/// This function searches for (table)
type RomTableLookupFn<T> = unsafe extern "C" fn(*const u16, u32) -> T;

/// The following addresses are described at `2.8.3. Bootrom Contents`
/// Pointer to the lookup table function supplied by the rom.
const ROM_TABLE_LOOKUP_PTR: *const u16 = 0x18 as _;

/// Pointer to helper functions lookup table.
const FUNC_TABLE: *const u16 = 0x14 as _;

/// Pointer to the public data lookup table.
const DATA_TABLE: *const u16 = 0x16 as _;

/// Retrive rom content from a table using a code.
fn rom_table_lookup<T>(table: *const u16, tag: RomFnTableCode) -> T {
    unsafe {
        let rom_table_lookup_ptr: *const u32 = rom_hword_as_ptr(ROM_TABLE_LOOKUP_PTR);
        let rom_table_lookup: RomTableLookupFn<T> = core::mem::transmute(rom_table_lookup_ptr);
        rom_table_lookup(rom_hword_as_ptr(table) as *const u16, u16::from_le_bytes(tag) as u32)
    }
}

unsafe fn rom_hword_as_ptr(rom_address: *const u16) -> *const u32 {
    let ptr: u16 = *rom_address;
    ptr as *const u32
}

macro_rules! rom_funcs {
    (
        $(
            $(#[$outer:meta])*
            $c:literal $name:ident (
                $( $aname:ident : $aty:ty ),*
            ) -> $ret:ty ;
        )*
    ) => {
        $(
            $(#[$outer])*
            pub fn $name($( $aname:$aty ),*) -> $ret{
                let func:  extern "C" fn( $( $aty ),* ) -> $ret = rom_table_lookup(FUNC_TABLE, *$c);
                func($( $aname ),*)
            }
        )*
    }
}

rom_funcs! {
    /// Return a count of the number of 1 bits in value.
    b"P3" popcount32(value: u32) -> u32;

    /// Return the bits of value in the reverse order.
    b"R3" reverse32(value: u32) -> u32;

    /// Return the number of consecutive high order 0 bits of value. If value is zero, returns 32.
    b"L3" clz32(value: u32) -> u32;

    /// Return the number of consecutive low order 0 bits of value. If value is zero, returns 32.
    b"T3" ctz32(value: u32) -> u32;

    /// Sets n bytes start at ptr to the value c and returns ptr
    b"MS" memset(ptr: *mut u8, c: u8, n: u8) -> *mut u8;

    /// Sets n bytes start at ptr to the value c and returns ptr. Note this is a slightly more
    /// efficient variant of _memset that may only be used if ptr is word aligned.
    b"M4" memset4(ptr: *mut u32, c: u8, n: u32) -> *mut u32;

    /// Copies n bytes starting at src to dest and returns dest. The results are undefined if the
    /// regions overlap.
    b"MC" memcpy(dest: *mut u8, src: *mut u8, n: u32) -> u8;

    /// Copies n bytes starting at src to dest and returns dest. The results are undefined if the
    /// regions overlap. Note this is a slightly more efficient variant of _memcpy that may only be
    /// used if dest and src are word aligned.
    b"C4" memcpy44(dest: *mut u32, src: *mut u32, n: u32) -> *mut u8;

    /// Restore all QSPI pad controls to their default state, and connect the SSI to the QSPI pads.
    b"IF" connect_internal_flash() -> ();

    /// First set up the SSI for serial-mode operations, then issue the fixed XIP exit sequence.
    /// Note that the bootrom code uses the IO forcing logic to drive the CS pin, which must be
    /// cleared before returning the SSI to XIP mode (e.g. by a call to _flash_flush_cache). This
    /// function configures the SSI with a fixed SCK clock divisor of /6.
    b"EX" flash_exit_xip() -> ();

    /// Erase a count bytes, starting at addr (offset from start of flash). Optionally, pass a
    /// block erase command e.g. D8h block erase, and the size of the block erased by this
    /// command — this function will use the larger block erase where possible, for much higher
    /// erase speed. addr must be aligned to a 4096-byte sector, and count must be a multiple of
    /// 4096 bytes.
    b"RE" flash_range_erase(addr: u32, count: usize, block_size: u32, block_cmd: u8) -> ();

    /// Program data to a range of flash addresses starting at addr (offset from the start of flash)
    /// and count bytesin size. addr must be aligned to a 256-byte boundary, and count must be a
    /// multiple of 256.
    b"RP" flash_range_program(addr: u32, data: *const u8, count: usize) -> ();

    /// Flush and enable the XIP cache. Also clears the IO forcing on QSPI CSn, so that the SSI can
    /// drive the flashchip select as normal.
    b"FC" flash_flush_cache() -> ();

    /// Configure the SSI to generate a standard 03h serial read command, with 24 address bits,
    /// upon each XIP access. This is a very slow XIP configuration, but is very widely supported.
    /// The debugger calls this function after performing a flash erase/programming operation, so
    /// that the freshly-programmed code and data is visible to the debug host, without having to
    /// know exactly what kind of flash device is connected.
    b"CX" flash_enter_cmd_xip() -> ();

    /// Resets the RP2040 and uses the watchdog facility to re-start in BOOTSEL mode:
    ///   * gpio_activity_pin_mask is provided to enable an 'activity light' via GPIO attached LED
    ///     for the USB Mass Storage Device:
    ///     * 0 No pins are used as per cold boot.
    ///     * Otherwise a single bit set indicating which GPIO pin should be set to output and
    ///       raised whenever there is mass storage activity from the host.
    ///  * disable_interface_mask may be used to control the exposed USB interfaces:
    ///    * 0 To enable both interfaces (as per cold boot).
    ///    * 1 To disable the USB Mass Storage Interface.
    ///    * 2 to Disable the USB PICOBOOT Interface.
    b"UB" reset_to_usb_boot(gpio_activity_pin_mask: u32, disable_interface_mask: u32) -> ();

    /// This is the method that is entered by core 1 on reset to wait to be launched by core 0.
    /// There are few cases where you should call this method (resetting core 1 is much better).
    /// This method does not return and should only ever be called on core 1.
    b"WV" wait_for_vector() -> !;
}

unsafe fn convert_str(s: *const u8) -> &'static str {
    let mut end = s;
    while *end != 0 {
        end = end.add(1);
    }
    let s = core::slice::from_raw_parts(s, end.offset_from(s) as usize);
    core::str::from_utf8_unchecked(s)
}

/// The Raspberry Pi Trading Ltd copyright string.
pub fn copyright_string() -> &'static str {
    let s: *const u8 = rom_table_lookup(DATA_TABLE, *b"CR");
    unsafe { convert_str(s) }
}

/// The 8 most significant hex digits of the Bootrom git revision.
pub fn git_revision() -> &'static str {
    let s: *const u8 = rom_table_lookup(DATA_TABLE, *b"GR");
    unsafe { convert_str(s) }
}

/// The start address of the floating point library code and data. This and fplib_end along with the individual
/// function pointers in soft_float_table can be used to copy the floating point implementation into RAM if
/// desired.
pub fn fplib_start() -> *const u8 {
    rom_table_lookup(DATA_TABLE, *b"FS")
}

/// See Table 181 for the contents of this table.
pub fn soft_float_table() -> *const u16 {
    rom_table_lookup(DATA_TABLE, *b"SF")
}

/// The end address of the floating point library code and data.
pub fn fplib_end() -> *const u8 {
    rom_table_lookup(DATA_TABLE, *b"FE")
}

/// This entry is only present in the V2 bootrom. See Table 182 for the contents of this table.
pub fn soft_double_table() -> *const u16 {
    rom_table_lookup(DATA_TABLE, *b"SD")
}

macro_rules! float_funcs {
    (
        $(
            $(#[$outer:meta])*
            $offset:literal $name:ident (
                $( $aname:ident : $aty:ty ),*
            ) -> $ret:ty;
        )*
    ) => {
        $(
            $(#[$outer])*
            pub fn $name() -> extern "C" fn( $( $aname : $aty ),* ) -> $ret {
                let table: *const *const u16 = rom_table_lookup(DATA_TABLE, *b"SF");
                unsafe {
                    core::mem::transmute_copy(&table.add($offset))
                }
            }
        )*
    }
}

float_funcs! {
    /// Return a + b.
    0x00 fadd(a: f32, b: f32) -> f32;
    /// Return a - b.
    0x04 fsub(a: f32, b: f32) -> f32;
    /// Return a * b.
    0x08 fmul(a: f32, b: f32) -> f32;
    /// Return a / b.
    0x0c fdiv(a: f32, b: f32) -> f32;
    /// Return the square root of v or -INFINITY if v is negative.
    0x18 fsqrt(v: f32) -> f32;
    /// Convert a float to a signed integer, rounding towards -INFINITY, and clamping the result
    /// to lie within the range -0x80000000 to 0x7FFFFFFF.
    0x1c float_to_int(v: f32) -> i32;
    /// Convert a float to a signed fixed point integer reprsentation where n specifies the
    /// position of the binary point in the resulting fixed point representation. e.g.
    /// float_to_fix(0.5, 16) == 0x8000. This method rounds towards -INFINITY, and clamps
    /// the resulting integer to lie within the range -800000000 to 0x7FFFFFFF.
    0x20 float_to_fix(v: f32, n: i32) -> i32;
    /// Convert a float to an unsigned integer, rounding towards -INFINITY, and clamping the result
    /// to lie within the range 0x00000000 to 0xFFFFFFFF
    0x24 float_to_uint(v: f32) -> u32;
    /// Convert a float to an unsigned fixed point integer representation where n specifies the
    /// position of the binary point in the resulting fixed point representation, e.g.
    /// float_to_ufix(0.5f, 16) == 0x8000. This method rounds towards -Infinity, and clamps the
    /// resulting integer to lie within the range 0x00000000 to 0xFFFFFFFF.
    0x28 float_to_ufix(v: f32, n: i32) -> u32;
    /// Convert a signed integer to the nearest float value, rounding to even on tie.
    0x2c int_to_float(v: i32) -> f32;
    /// Convert a signed fixed point integer representation to the nearest float value, rounding
    /// to even on tie. n specifies the position of the binary point in fixed point, so
    /// f = nearest(v/2^n).
    0x30 fix_to_float(v: i32, n: i32) -> f32;
    /// Convert an unsigned integer to the nearest float value, rounding to even on tie.
    0x34 uint_to_float(v: u32) -> f32;
    /// Convert a unsigned fixed point integer representation to the nearest float value, rounding
    /// to even on tie. n specifies the position of the binary point in fixed point, so
    /// f = nearest(v/2^n).
    0x38 ufix_to_float(v: u32, n: i32) -> f32;
    /// Return the cosine of angle. angle is in radians, and must be in the range -128 to 128.
    0x3c fcos(angle: f32) -> f32;
    /// Return the sine of angle. angle is in radians, and must be in the range -128 to 128.
    0x40 fsin(angle: f32) -> f32;
    /// Return the tangent of angle. angle is in radians, and must be in the range -128 to 128.
    0x44 ftan(angle: f32) -> f32;
    /// Return the exponential value of v, i.e. so e^v.
    0x4c fexp(v: f32) -> f32;
    /// Return the natural logarithm of v. If v <= 0 return -Infinity.
    0x50 fln(v: f32) -> f32;
    /// Compares two floating point numbers, returning:
    ///   * 0 if a == b
    ///   * -1 if a < b
    ///   * 1 if a > b
    0x54 fcmp(a: f32, b: f32) -> i32;
    /// Computes the arc tangent of y/x using the signs of arguments to determine the correct quadrant.
    0x58 fatan2(y: f32, x: f32) -> f32;
    /// Convert a signed 64-bit integer to the nearest float value, rounding to even on tie.
    0x5c int64_to_float(v: i64) -> f32;
    /// Convert a signed fixed point integer representation to the nearest float value, rounding
    /// to even on tie. n specifies the position of the binary point in fixed point, so
    /// f = nearest(v/2^n).
    0x60 fix64_to_float(v: i64, n: i32) -> f32;
    /// Convert an unsigned 64-bit integer to the nearest float value, rounding to even on tie.
    0x64 uint64_to_float(v: u64) -> f32;
    /// Convert an unsigned fixed point integer representation to the nearest float value, rounding
    /// to even on tie. n specifies the position of the binary point in fixed point, so
    /// f = nearest(v/2^n).
    0x68 ufix64_to_float(v: u64, n: i32) -> f32;
    /// Convert a float to a signed 64-bit integer, rounding towards -Infinity, and clamping
    /// the result to lie within the range -0x8000000000000000 to 0x7FFFFFFFFFFFFFFF
    0x6c float_to_int64(v: f32) -> i64;
    ///     Convert a float to a signed fixed point 64-bit integer representation where n
    /// specifies the position of the binary point in the resulting fixed point representation -
    /// e.g. _float2fix(0.5f, 16) == 0x8000. This method rounds towards -Infinity, and
    /// clamps the resulting integer to lie within the range -0x8000000000000000 to
    /// 0x7FFFFFFFFFFFFFF
    0x70 float_to_fix64(v: f32, n: i32) -> f32;
    /// Convert a float to an unsigned 64-bit integer, rounding towards -Infinity, and
    /// clamping the result to lie within the range 0x0000000000000000 to 0xFFFFFFFFFFFFFFFF
    0x74 float_to_uint64(v: f32) -> u64;
    /// Convert a float to an unsigned fixed point 64-bit integer representation where n
    /// specifies the position of the binary point in the resulting fixed point representation,
    /// e.g. _float2ufix(0.5f, 16) == 0x8000. This method rounds towards -Infinity, and
    /// clamps the resulting integer to lie within the range 0x0000000000000000 to
    /// 0xFFFFFFFFFFFFFFFF
    /// 0x78 float_to_ufix64(v: f32, n: i32) -> u64;
    /// Converts a float to a double.
    0x7c float_to_double(v: f32) -> f64;
}

macro_rules! double_funcs {
    (
        $(
            $(#[$outer:meta])*
            $offset:literal $name:ident (
                $( $aname:ident : $aty:ty ),*
            ) -> $ret:ty;
        )*
    ) => {
        $(
            $(#[$outer])*
            pub fn $name() -> extern "C" fn( $( $aname : $aty ),* ) -> $ret {
                let table: *const *const u16 = rom_table_lookup(DATA_TABLE, *b"SD");
                unsafe {
                    core::mem::transmute_copy(&table.add($offset))
                }
            }
        )*
    }
}

double_funcs! {
    /// Return a + b
    0x00 dadd(a: f64, b: f64) -> f64;
    /// Return a - b
    0x04 dsub(a: f64, b: f64) -> f64;
    /// Return a * b
    0x08 dmul(a: f64, b: f64) -> f64;
    /// Return a / b
    0x0c ddiv(a: f64, b: f64) -> f64;
    /// Return sqrt(v) or -Infinity if v is negative
    0x18 dsqrt(v: f64) -> f64;
    /// Convert a double to a signed integer, rounding towards -Infinity, and clamping the result to lie
    /// within the range -0x80000000 to 0x7FFFFFFF
    0x1c double_to_int(v: f64) -> i32;
    /// Convert a double to an unsigned fixed point integer representation where n specifies the
    /// position of the binary point in the resulting fixed point representation, e.g. _double2ufix(0.5f,
    /// 16) == 0x8000. This method rounds towards -Infinity, and clamps the resulting integer to lie
    /// within the range 0x00000000 to 0xFFFFFFFF
    0x20 double_to_fix(v: f64, n: i32) -> i32;
    /// Convert a double to an unsigned integer, rounding towards -Infinity, and clamping the result
    /// to lie within the range 0x00000000 to 0xFFFFFFFF    0x24 double_to_uint(v: f64) -> u32;
    0x28 double_to_ufix(v: f64, n: i32) -> u32;
    /// Convert a signed integer to the nearest double value, rounding to even on tie
    0x2c int_to_double(v: i32) -> f64;
    /// Convert a signed fixed point integer representation to the nearest double value, rounding to
    /// even on tie. n specifies the position of the binary point in fixed point, so f = nearest(v/(2^n))
    0x30 fix_to_double(v: i32, n: i32) -> f64;
    /// Convert an unsigned integer to the nearest double value, rounding to even on tie
    0x34 uint_to_double(v: u32) -> f64;
    /// Convert an unsigned fixed point integer representation to the nearest double value, rounding
    /// to even on tie. n specifies the position of the binary point in fixed point, so
    /// f = nearest(v/(2^n))
    0x38 ufix_to_double(v: u32, n: i32) -> f64;
    /// Return the cosine of angle. angle is in radians, and must be in the range -1024 to 1024
    0x3c dcos(angle: f64) -> f64;
    /// Return the sine of angle. angle is in radians, and must be in the range -1024 to 1024
    0x40 dsin(angle: f64) -> f64;
    /// Return the tangent of angle. angle is in radians, and must be in the range -1024 to 1024
    0x44 dtan(angle: f64) -> f64;
    /// Return the exponential value of v, i.e. so 
    0x4c dexp(v: f64) -> f64;
    /// Return the natural logarithm of v. If v <= 0 return -Infinity
    0x50 dln(v: f64) -> f64;
    /// Compares two floating point numbers, returning:
    ///     • 0 if a == b
    ///     • -1 if a < b
    ///     • 1 if a > b
    0x54 dcmp(a: f64, b: f64) -> i32;
    /// Computes the arc tangent of y/x using the signs of arguments to determine the correct
    /// quadrant
    0x58 datan2(y: f64, x: f64) -> f64;
    /// Convert a signed 64-bit integer to the nearest double value, rounding to even on tie
    0x5c int64_to_double(v: i64) -> f64;
    /// Convert a signed fixed point 64-bit integer representation to the nearest double value,
    /// rounding to even on tie. n specifies the position of the binary point in fixed point, so
    /// f = nearest(v/(2^n))
    0x60 fix64_to_doubl(v: i64, n: i32) -> f64;
    /// Convert an unsigned 64-bit integer to the nearest double value, rounding to even on tie
    0x64 uint64_to_double(v: u64) -> f64;
    /// Convert an unsigned fixed point 64-bit integer representation to the nearest double value,
    /// rounding to even on tie. n specifies the position of the binary point in fixed point, so
    /// f = nearest(v/(2^n))
    0x68 ufix64_to_double(v: u64, n: i32) -> f64;
    /// Convert a double to a signed 64-bit integer, rounding towards -Infinity, and
    0x6c double_to_int64(v: f64) -> i64;
    /// Convert a double to a signed fixed point 64-bit integer representation where n specifies the
    /// position of the binary point in the resulting fixed point representation - e.g. _double2fix(0.5f,
    /// 16) == 0x8000. This method rounds towards -Infinity, and clamps the resulting integer to lie
    /// within the range -0x8000000000000000 to 0x7FFFFFFFFFFFFFFF    
    0x70 double_to_fix64(v: f64, n: i32) -> i64;
    /// Convert a double to an unsigned 64-bit integer, rounding towards -Infinity, and clamping the
    /// result to lie within the range 0x0000000000000000 to 0xFFFFFFFFFFFFFFFF
    0x74 double_to_uint64(v: f64) -> u64;
    /// Convert a double to an unsigned fixed point 64-bit integer representation where n specifies
    /// the position of the binary point in the resulting fixed point representation, e.g.
    /// _double2ufix(0.5f, 16) == 0x8000. This method rounds towards -Infinity, and clamps the
    /// resulting integer to lie within the range 0x0000000000000000 to 0xFFFFFFFFFFFFFFFF
    0x78 double_to_ufix64(v: f64, n: i32) -> u64;
    /// Converts a double to a float
    0x7c double_to_float(v: f64) -> f32;
}