Pillow

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/*
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 * The Python Imaging Library.
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 * $Id$
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 *
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 * decoder for XBM hex image data
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 *
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 * history:
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 * 96-04-13 fl Created
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 *
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 * Copyright (c) Fredrik Lundh 1996.
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 * Copyright (c) Secret Labs AB 1997.
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 *
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 * See the README file for information on usage and redistribution.
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 */
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#include "Imaging.h"
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#define HEX(v)                               \
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    ((v >= '0' && v <= '9')   ? v - '0'      \
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     : (v >= 'a' && v <= 'f') ? v - 'a' + 10 \
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     : (v >= 'A' && v <= 'F') ? v - 'A' + 10 \
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                              : 0)
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int
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ImagingXbmDecode(Imaging im, ImagingCodecState state, UINT8 *buf, Py_ssize_t bytes) {
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    enum { BYTE = 1, SKIP };
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    UINT8 *ptr;
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    if (!state->state) {
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        state->state = SKIP;
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    }
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    ptr = buf;
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    for (;;) {
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        if (state->state == SKIP) {
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            /* Skip forward until next 'x' */
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            while (bytes > 0) {
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                if (*ptr == 'x') {
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                    break;
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                }
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                ptr++;
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                bytes--;
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            }
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            if (bytes == 0) {
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                return ptr - buf;
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            }
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            state->state = BYTE;
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        }
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        if (bytes < 3) {
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            return ptr - buf;
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        }
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        state->buffer[state->x] = (HEX(ptr[1]) << 4) + HEX(ptr[2]);
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        if (++state->x >= state->bytes) {
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            /* Got a full line, unpack it */
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            state->shuffle((UINT8 *)im->image[state->y], state->buffer, state->xsize);
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            state->x = 0;
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            if (++state->y >= state->ysize) {
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                /* End of file (errcode = 0) */
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                return -1;
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            }
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        }
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        ptr += 3;
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        bytes -= 3;
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        state->state = SKIP;
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    }
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}
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