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Lexikon

btoa

/B too A/ A href="module.php?name=Lexikon&file=search&eid=1&query=binary">binary to href="module.php?name=Lexikon&file=search&eid=1&query=ASCII">ASCII conversion utility. btoa is a href="module.php?name=Lexikon&file=search&eid=1&query=uuencode">uuencode or href="module.php?name=Lexikon&file=search&eid=1&query=base 64">base 64 equivalent which addresses some of the problems with the uuencode standard but not as many as the base 64 standard. It avoids problems that some href="module.php?name=Lexikon&file=search&eid=1&query=hosts">hosts have with spaces (e.g. conversion of groups of spaces to tabs) by not including them in its character set, but may still have problems on non-ASCII systems (e.g. href="module.php?name=Lexikon&file=search&eid=1&query=EBCDIC">EBCDIC). btoa is primarily used to transfer href="module.php?name=Lexikon&file=search&eid=1&query=binary files">binary files between systems across connections which are not href="module.php?name=Lexikon&file=search&eid=1&query=eight-bit clean">eight-bit clean, e.g. href="module.php?name=Lexikon&file=search&eid=1&query=electronic mail">electronic mail. btoa takes adjacent sets of four binary href="module.php?name=Lexikon&file=search&eid=1&query=octets">octets and encodes them as five ASCII href="module.php?name=Lexikon&file=search&eid=1&query=octets">octets using ASCII characters ' !' through to ' u' . Special characters are also used: ' x' marks the beginning or end of the archive ' z' marks four consecutive zeros and ' y' (version 5.2) four consecutive spaces. Each group of four octets is processed as a 32-bit integer. Call this ' I' . Let ' D' = 85^4. Divide I by D. Call this result ' R' . Make I = I - (R * D) to avoid href="module.php?name=Lexikon&file=search&eid=1&query=overflow">overflow on the next step. Repeat, for values of D = 85^3, 85^2, 85 and 1. At each step, to convert R to the output character add decimal 33 (output octet = R + ASCII value for ' !' ). Five output octets are produced. btoa provides some integrity checking in the form of a line href="module.php?name=Lexikon&file=search&eid=1&query=checksum">checksum, and facilities for patching corrupted downloads. The href="module.php?name=Lexikon&file=search&eid=1&query=algorithm">algorithm used by btoa is more efficient than uuencode or base 64. ASCII files are encoded to about 120% the size of their binary sources. This compares with 135% for uuencode or base 64. href="ftp://hpux.csc.liv.ac.uk/hpux/Misc/btoa-5.2/">C source . (version 5.2 - ~1994). Pre-compiled href="module.php?name=Lexikon&file=search&eid=1&query=MS-DOS">MS-DOS versions are also available. (1997-08-08)

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