hvfsmaker.py

#!/usr/bin/python

import sys, os, zlib, io
from struct import pack, unpack

if (len(sys.argv) > 1):
    hvfsdir  = sys.argv[1]
else:
    print "Use: hvfsmaker.py directory"
    sys.exit(0)

f = open("hvfs.fs", "w+b")

# Start creating our file
f.write("HvFs")

numfiles = 0
totsize = 0
totlen = 0

files = []

banner = "Tilera Hypervisor file system by ME!"
totlen += (4 - (len(banner)%4)) + len(banner)

for name in sorted(os.listdir(hvfsdir)):
    long = os.path.join(hvfsdir, name)
    filerealsize = os.stat(long).st_size
    filesize_align = (4 - (filerealsize%4)) + filerealsize
    namelen = (4 - (len(name)%4)) + len(name)
    numfiles += 1
    totsize += filerealsize
    totlen += namelen
    files.append((name,namelen,filesize_align,long,filerealsize))

# (4_HVFS + 16_HEADER + ( 16_INODE * FILES))
namebase = 4 + 16 + (16 * numfiles)

# (NAMEBASE + lenght of all filenames, keeping 1 char empty per name)
filebase = namebase + totlen

print "Files to add %d" % numfiles
print "Size to add %d" % totsize
print "Starting names at %d" % namebase
print "Starting files at %d" % filebase

# Leave header empty for now
f.seek(16,1)

# Inserting banner, it's the first entry at namebase
currentpos = f.tell()
f.seek(namebase,0)
f.write(banner)
namebase += len(banner)+1
f.seek(currentpos,0)

print "Writing inodes and files"
for file in files:
    print "Injecting file %s:name at %d and file at %d" % (file[0], namebase, filebase)
    # POS without 4_HVFS ident
    f.write(pack('<IIII', (namebase-4), (filebase-4), file[4], 0))
    currentpos = f.tell()

    # Put filename in the right place (empty trailer)
    f.seek(namebase,0)
    f.write(file[0])

    # Copy data from our file into HVFS
    f.seek(filebase,0)
    copy = file[4]
    f2 = open(file[3],'rb')
    while copy:
        block = min(1024,copy)
        data = f2.read(block)
        f.write(data)
        copy -= block
    f2.close()

    # Go back for the next file / inode
    f.seek(currentpos,0)
    namebase += file[1]
    filebase += file[2]

f.seek(0, io.SEEK_END)
fsend = f.tell()
print "done with inodes and files at %d" % fsend

# FS CRC might need to shift, create empty space if necessary (nasty hack)
if (fsend-4)%4 != 0 :
    fsend += (4 - (fsend-4)%4)
    f.seek(fsend,0)
    f.write(pack("<I", 0))

# Calculate and write header CRC (pos 5-20, we left this space empty)
f.seek(4,0)
headercrc = zlib.crc32(pack('<ccccIII',"H", "v", "F", "s", numfiles, (fsend-4), (16 + (16 * numfiles)))) & 0xffffffff
f.write(pack('<IIII', numfiles, (fsend-4), (16 + (16 * numfiles)), headercrc))

# Filesystem (skip 4_HVFS + 16_HEADER) (end of file)
f.seek(20,0)
fscrc = zlib.crc32(f.read(fsend-20)) & 0xffffffff
f.seek(fsend,0)
f.write(pack("<I", fscrc))

print "Header CRC: %X" % headercrc
print "Filesystem CRC: %X" % fscrc

f.close()