[woff2] Reconstruct `loca', `hmtx', and swap out stream.

Add necessary functions to reconstruct loca and hmtx tables (the two
remaining tables that can have a transform).  `woff2_open_font' is
now capable of loading a woff2 font face.  This code may still need
more refining and better memory management.

* include/freetype/internal/wofftypes.h (WOFF2_HeaderRec): Add total
(final) size of sfnt stream.

(WOFF2_InfoRec): Add header checksum value.

* src/sfnt/sfobjs.c (sfnt_open_font): Change `face_instance_index'
parameter to its pointer so its value can be modified by

* src/sfnt/sfwoff2.c: (WRITE_SFNT_BUF_AT): New macro to write into
sfnt buffer at given position.

(write_buf): Add parameter `extend_buf' which allows caller to
specify whether buffer should be reallocated before copying data.

(WRITE_SFNT_BUF): Updated.

(pad4, store_loca, reconstruct_htmx): New functions.

(reconstruct_glyf): Calculate loca values and store them.

(reconstruct_font): Call `reconstruct_hmtx', write table record
entries, and calculate table checksums.  Also calculate font
checksum and update `checksumAdjustment' entry in head table.

(woff2_open_font): Open stream for sfnt buffer, swap out input
stream and return.

* src/sfnt/sfwoff2.h (woff2_open_font): Modify parameter to accept
pointer to `face_index'.
5 files changed