| 1 | /* ----------------------------------------------------------------------- * |
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| 2 | * |
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| 3 | * Copyright 2007-2009 H. Peter Anvin - All Rights Reserved |
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| 4 | * Copyright 2009 Intel Corporation; author: H. Peter Anvin |
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| 5 | * |
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| 6 | * This program is free software; you can redistribute it and/or modify |
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| 7 | * it under the terms of the GNU General Public License as published by |
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| 8 | * the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, |
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| 9 | * Boston MA 02110-1301, USA; either version 2 of the License, or |
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| 10 | * (at your option) any later version; incorporated herein by reference. |
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| 11 | * |
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| 12 | * ----------------------------------------------------------------------- */ |
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| 13 | |
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| 14 | /* |
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| 15 | * rllpack.inc |
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| 16 | * |
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| 17 | * Very simple RLL compressor/decompressor, used to pack binary structures |
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| 18 | * together. |
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| 19 | * |
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| 20 | * Format of leading byte |
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| 21 | * 1-128 = x verbatim bytes follow |
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| 22 | * 129-223 = (x-126) times subsequent byte |
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| 23 | * 224-255 = (x-224)*256+(next byte) times the following byte |
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| 24 | * 0 = end of data |
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| 25 | * |
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| 26 | * These structures are stored *in reverse order* in high memory. |
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| 27 | * High memory pointers point to one byte beyond the end. |
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| 28 | */ |
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| 29 | |
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| 30 | #include <com32.h> |
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| 31 | #include <stddef.h> |
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| 32 | #include <string.h> |
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| 33 | |
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| 34 | void rllpack(com32sys_t * regs) |
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| 35 | { |
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| 36 | uint8_t *i = (uint8_t *) (regs->esi.l); |
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| 37 | uint8_t *o = (uint8_t *) (regs->edi.l); |
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| 38 | size_t cnt = regs->ecx.l; |
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| 39 | size_t run, vrun, tcnt; |
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| 40 | uint8_t *hdr = NULL; |
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| 41 | uint8_t c; |
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| 42 | |
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| 43 | vrun = (size_t)-1; |
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| 44 | while (cnt) { |
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| 45 | c = *i; |
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| 46 | |
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| 47 | run = 1; |
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| 48 | tcnt = (cnt > 8191) ? 8191 : cnt; |
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| 49 | while (run < tcnt && i[run] == c) |
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| 50 | run++; |
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| 51 | |
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| 52 | if (run < 3) { |
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| 53 | if (vrun >= 128) { |
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| 54 | hdr = --o; |
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| 55 | vrun = 0; |
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| 56 | } |
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| 57 | *--o = c; |
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| 58 | *hdr = ++vrun; |
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| 59 | i++; |
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| 60 | cnt--; |
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| 61 | } else { |
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| 62 | if (run < 224 - 126) { |
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| 63 | *--o = run + 126; |
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| 64 | } else { |
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| 65 | o -= 2; |
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| 66 | *(uint16_t *) o = run + (224 << 8); |
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| 67 | } |
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| 68 | *--o = c; |
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| 69 | vrun = (size_t)-1; |
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| 70 | i += run; |
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| 71 | cnt -= run; |
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| 72 | } |
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| 73 | } |
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| 74 | *--o = 0; |
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| 75 | |
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| 76 | regs->esi.l = (size_t)i; |
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| 77 | regs->edi.l = (size_t)o; |
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| 78 | } |
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| 79 | |
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| 80 | void rllunpack(com32sys_t * regs) |
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| 81 | { |
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| 82 | uint8_t *i = (uint8_t *) regs->esi.l; |
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| 83 | uint8_t *o = (uint8_t *) regs->edi.l; |
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| 84 | uint8_t c; |
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| 85 | size_t n; |
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| 86 | |
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| 87 | while ((c = *--i)) { |
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| 88 | if (c <= 128) { |
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| 89 | while (c--) |
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| 90 | *o++ = *--i; |
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| 91 | } else { |
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| 92 | if (c < 224) |
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| 93 | n = c - 126; |
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| 94 | else |
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| 95 | n = ((c - 224) << 8) + *--i; |
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| 96 | c = *--i; |
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| 97 | while (n--) |
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| 98 | *o++ = c; |
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| 99 | } |
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| 100 | } |
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| 101 | |
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| 102 | regs->esi.l = (size_t)i; |
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| 103 | regs->ecx.l = (size_t)o - regs->edi.l; |
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| 104 | regs->edi.l = (size_t)o; |
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| 105 | } |
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