CTR Font Format

.bcfnt files are bitmap fonts made for the 3ds. The system font uses this format too except the header is changed from CFNT to CFNU and all file offsets are changed to absolute in memory offsets.

CFNT Header

Offset	Size	Description
0x00	0x04	Magic Header (either CFNT or CFNU or FFNT)
0x04	0x02	Endianness (0xFEFF = little, 0xFFFE = big)
0x06	0x02	Header Size
0x08	0x04	Version (observed to be 0x03000000)
0x0C	0x04	File size (the total)
0x10	0x04	Number of "blocks" to read

FINF Header

Version 3 (BCFNT)

Offset	Size	Description
0x00	0x04	Magic Header (FINF)
0x04	0x04	Section Size
0x08	0x01	Font Type
0x09	0x01	Line Feed
0x0A	0x02	Alter Char Index
0x0C	0x03	Default Width (3 bytes: Left, Glyph Width, Char Width)
0x0F	0x01	Encoding
0x10	0x04	TGLP Offset
0x14	0x04	CWDH Offset
0x18	0x04	CMAP Offset
0x1C	0x01	Height
0x1D	0x01	Width
0x1E	0x01	Ascent
0x1F	0x01	Reserved

Version 4 (BFFNT)

Offset	Size	Description
0x00	0x04	Magic Header (FINF)
0x04	0x04	Section Size
0x08	0x01	Font Type
0x09	0x01	Height
0x0A	0x01	Width
0x0B	0x01	Ascent
0x0C	0x02	Line Feed
0x0E	0x02	Alter Char Index
0x10	0x03	Default Width (3 bytes: Left, Glyph Width, Char Width)
0x13	0x01	Encoding
0x14	0x04	TGLP Offset
0x18	0x04	CWDH Offset
0x1C	0x04	CMAP Offset

TGLP Header

Version 3 (BCFNT)

Offset	Size	Description
0x00	0x04	Magic Header (TGLP)
0x04	0x04	Section Size
0x08	0x01	Cell Width
0x09	0x01	Cell Height
0x0A	0x01	Baseline Position
0x0B	0x01	Max Character Width
0x0C	0x04	Sheet Size
0x10	0x02	Number of Sheets
0x12	0x02	Sheet Image Format 0-13: (RGBA8, RGB8, RGBA5551, RGB565, RGBA4, LA8, HILO8, L8, A8, LA4, L4, A4, ETC1, ETC1A4)
0x14	0x02	Number of Sheet rows
0x16	0x02	Number of Sheet lines
0x18	0x02	Sheet Width
0x1A	0x02	Sheet Height
0x1C	0x04	Sheet Data Offset

Version 4 (BFFNT)

Offset	Size	Description
0x00	0x04	Magic Header (TGLP)
0x04	0x04	Section Size
0x08	0x01	Cell Width
0x09	0x01	Cell Height
0x0A	0x01	Number of Sheets
0x0B	0x01	Max Character Width
0x0C	0x04	Sheet Size
0x10	0x02	Baseline Position
0x12	0x02	Sheet Image Format 0-13: (RGBA8, RGB8, RGBA5551, RGB565, RGBA4, LA8, HILO8, L8, A8, LA4, L4, A4, ETC1, ETC1A4)
0x14	0x02	Number of Sheet rows
0x16	0x02	Number of Sheet lines
0x18	0x02	Sheet Width
0x1A	0x02	Sheet Height
0x1C	0x04	Sheet Data Offset

CMAP Header

Offset	Size	Description
0x00	0x04	Magic Header (CMAP)
0x04	0x04	Section Size
0x08	0x02	Code Begin
0x0A	0x02	Code End
0x0C	0x02	Mapping Method (0 = Direct, 1 = Table, 2 = Scan)
0x0E	0x02	Reserved?
0x10	0x04	Next CMAP Offset

Depending on the mapping method the next bytes are read like so:

Direct: IndexOffset = read uint16

Table: IndexTable = read uint16 array (CodeEnd - CodeBegin + 1)

Scan: Number of Scan Entries = read uint16 for every scan entry: read uint16 & read uint16

CWDH Header

Offset	Size	Description
0x00	0x04	Magic Header (CWDH)
0x04	0x04	Section Size
0x08	0x02	Start Index
0x0A	0x02	End Index
0x0C	0x04	Next CWDH Offset
0x10	3 * (EndIndex - StartIndex + 1)	Char Widths (3 bytes: Left, Glyph Width, Char Width)