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/*
* lzw.c
* Euman = ∫(optimization/time) △ performance
*
* @file lzw.c @version 2.1.0
* @author H. Overman (ee)
* @created 2026-03-20
* @modified 2026-03-20
* @by H. Overman (ee)
* @brief LZW compression / decompression. C23
* Direct-index dict: dict[code].next[byte] = next_code.
* O(1) lookup. Zero collision possible.
* Sentinel EE_LZW_EMPTY = 0xFFFF (exceeds all valid codes).
* Self-tests at startup. Gate-X at structural cause.
*
* Build (release): gcc -O3 -march=native -flto -funroll-loops -DNDEBUG
* -Wall -Wextra -Wpedantic lzw.c -o lzw
* Build (ASan): gcc -fsanitize=address,undefined -O1 -g
* -Wall -Wextra -Wpedantic lzw.c -o lzw
*
* Usage:
* ./lzw test -- run self-tests and test suite
* ./lzw -- interactive (==comp / ==decomp)
*
*
* =======================================================================
* IFP INVARIANTS (causal order)
* =======================================================================
*
* I1: dict(code, byte) -> next_code
* Direct array: ee_lzw_entry_t.next[byte]. O(1). Zero collision.
* Sentinel: EE_LZW_EMPTY = 0xFFFF. Never a valid code since
* EE_LZW_DICT_MAX = 4096 < 0xFFFF.
* Spot-check: 'A'=0x41, next['B'=0x42] = 256 after first "AB"
* added. dict[0x41].next[0x42] == 256. Verified in self-test.
*
* I2: compress(input, len) -> {codes[], code_count}
* Walk input. I1 lookup each byte.
* Hit: extend current code. Miss: emit, add entry, reset.
* Emit final code after loop.
*
* I3: decompress(codes[], count) -> {output[], out_len}
* Rebuild dict incrementally. Invert I2 exactly.
* Special case: code == dict_size (string ends with own first char).
*
* I4: round-trip invariant
* decompress(compress(s)) == s for all valid inputs.
* Verified by self-test checks 7-8.
*
* =======================================================================
* DICT STRUCTURE
* =======================================================================
*
* Direct-index: next[byte] = next_code or EE_LZW_EMPTY.
* Key = byte. Value = next_code. No hash. No probe. No collision.
* sizeof(ee_lzw_entry_t) = 256 * 2 = 512 bytes per entry.
* Total dict = 4096 * 512 = 2 097 152 bytes = 2 MB.
*
* Derivation (python3):
* entries = 4096; entry_sz = 256 * 2; total = entries * entry_sz
* print(total) # -> 2097152
* Spot-check: 4096 * 512 = 2 097 152. Exact.
*
* =======================================================================
* SENTINEL DERIVATION
* =======================================================================
*
* EE_LZW_EMPTY = 0xFFFF = 65535.
* EE_LZW_DICT_MAX = 4096. Valid codes: [0, 4095].
* 65535 > 4095. Never a valid code. Unambiguous empty marker.
* 0xFF fill (memset) sets every uint16_t slot to 0xFFFF. One call.
* Using 0 as sentinel (original) was wrong: code 0 = NUL byte,
* a valid single-character literal. 0xFFFF is structurally safe.
*
* =======================================================================
* ACKNOWLEDGMENTS
* =======================================================================
*
* H. Overman (ee):
* ppo-2 C23 systems programming standard. 4-state gate Z/X/0/1.
* FRONT/LEAD/REAR. IFP. ExCLisp. Direct-index dict.
* EE_LZW_EMPTY sentinel design. Linux kernel style.
*
* Terry Welch (IEEE Computer, June 1984):
* "A Technique for High-Performance Data Compression."
* LZW algorithm. Dictionary-based compression.
*
* Abraham Lempel / Jacob Ziv (1977, 1978):
* LZ77 / LZ78 -- precursors to LZW.
*
* ==================================================================
*/
#define _POSIX_C_SOURCE 200809L
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <inttypes.h>
#include <time.h>
/*
* ==================================================================
* LOGOS / CONSTANTS
* ==================================================================
*/
/*
* EE_LZW_DICT_MAX = 4096 = 2^12.
* Standard LZW 12-bit code space. Codes [0,255]: literals.
* Codes [256, 4095]: runtime extensions. 3840 extension slots.
*/
#define EE_LZW_DICT_MAX 4096u
#define EE_LZW_ALPHA_SZ 256u /* byte alphabet 2^8 */
#define EE_LZW_CODES_MAX 10000u /* max codes per compress pass */
#define EE_LZW_OUTPUT_MAX 20000u /* max bytes per decompress pass */
#define EE_LZW_STR_MAX 256u /* max length of one dict string */
/*
* EE_LZW_EMPTY = 0xFFFF = 65535.
* Derivation: EE_LZW_DICT_MAX = 4096. Valid codes [0, 4095].
* 0xFFFF = 65535 > 4095. Never a valid code. Safe sentinel.
* memset(dict, 0xFF, ...) initialises all slots to 0xFFFF in one call.
*/
#define EE_LZW_EMPTY 0xFFFFu
static_assert(EE_LZW_DICT_MAX == 4096u,
"dict max must be 4096");
static_assert(EE_LZW_ALPHA_SZ == 256u,
"alpha must be 256");
static_assert(EE_LZW_EMPTY > EE_LZW_DICT_MAX - 1u,
"sentinel must exceed all valid codes");
static_assert(EE_LZW_DICT_MAX * EE_LZW_ALPHA_SZ * sizeof(uint16_t) == 2097152u,
"dict total size must be 2097152 bytes");
/*
* ==================================================================
* LOGOS / 4-STATE GATE CONSTANTS
* ==================================================================
*/
#define EE_GATE_Z 0x00u /* not applicable: empty input */
#define EE_GATE_X 0x01u /* error: overflow, invalid code, NULL ptr */
#define EE_GATE_0 0x02u /* deny: invariant violation */
#define EE_GATE_1 0x03u /* allow: success */
static_assert(EE_GATE_Z != EE_GATE_X &&
EE_GATE_X != EE_GATE_0 &&
EE_GATE_0 != EE_GATE_1,
"gate constants must be distinct");
/*
* ==================================================================
* LOGOS / REASON CODES
* ==================================================================
*/
#define EE_LZW_OK 0x0000u
#define EE_LZW_R_EMPTY 0x0001u /* gate-Z: empty input */
#define EE_LZW_R_NULL 0x0002u /* gate-X: required ptr NULL */
#define EE_LZW_R_CODES_OVF 0x0003u /* gate-X: code output overflow */
#define EE_LZW_R_OUTPUT_OVF 0x0004u /* gate-X: byte output overflow */
#define EE_LZW_R_BAD_CODE 0x0005u /* gate-X: code > dict_size */
#define EE_LZW_R_STR_OVF 0x0006u /* gate-X: string length overflow */
#define EE_LZW_R_DICT_FULL 0x0007u /* gate-0: dict at capacity */
#define EE_LZW_R_SELF_FAIL 0x000Fu /* gate-0: self-test failure */
/*
* ==================================================================
* LOGOS / GATE RESULT
* ==================================================================
*/
/*
* ee_lzw_gate_t
*
* Universal return type. Every public function returns this.
* Gate-X fires at the structural cause -- not at the symptom.
*/
typedef struct ee_lzw_gate {
uint8_t state;
uint8_t pad;
uint16_t reason;
} ee_lzw_gate_t;
static_assert(sizeof(ee_lzw_gate_t) == 4u, "gate must be 4 bytes");
/*
* ==================================================================
* LOGOS / DICT ENTRY (I1)
*
* Direct-index: next[byte] = next_code or EE_LZW_EMPTY.
* O(1). Zero collision possible. Byte IS the index.
* ==================================================================
*/
typedef struct ee_lzw_entry {
uint16_t next[EE_LZW_ALPHA_SZ]; /* 256 x 2 = 512 bytes */
} ee_lzw_entry_t;
static_assert(sizeof(ee_lzw_entry_t) == 512u,
"dict entry must be 512 bytes");
/*
* ==================================================================
* LOGOS / COMPRESS STATE (I2)
* ==================================================================
*/
typedef struct ee_lzw_cs {
ee_lzw_entry_t dict[EE_LZW_DICT_MAX]; /* I1 direct-index dict */
uint16_t codes[EE_LZW_CODES_MAX];/* output code sequence */
uint32_t dict_size; /* current dict entries */
uint32_t code_count; /* codes emitted */
} ee_lzw_cs_t;
/*
* ==================================================================
* LOGOS / DECOMPRESS STATE (I3)
* ==================================================================
*/
typedef struct ee_lzw_str {
uint8_t data[EE_LZW_STR_MAX];
uint16_t len;
} ee_lzw_str_t;
static_assert(sizeof(ee_lzw_str_t) == EE_LZW_STR_MAX + 2u,
"lzw_str_t must be EE_LZW_STR_MAX + 2 bytes");
typedef struct ee_lzw_ds {
ee_lzw_str_t str[EE_LZW_DICT_MAX];
uint8_t output[EE_LZW_OUTPUT_MAX];
uint32_t dict_size;
uint32_t out_len;
} ee_lzw_ds_t;
/*
* ==================================================================
* LOGOS COMPLETE. LOGIC begins below.
* ==================================================================
*/
static inline ee_lzw_gate_t
lzw__ok(void)
{
return (ee_lzw_gate_t){ EE_GATE_1, 0u, EE_LZW_OK };
}
static inline ee_lzw_gate_t
lzw__gate(uint8_t state, uint16_t reason)
{
return (ee_lzw_gate_t){ state, 0u, reason };
}
/*
* ==================================================================
* LOGIC / COMPRESS INIT
* ==================================================================
*/
/*
* lzw_compress_init
*
* FRONT: uninitialised cs (AS)
* LEAD: memset(0xFF) sets all next[] slots to EE_LZW_EMPTY;
* dict_size = 256; code_count = 0 (Pivot)
* REAR: cs ready for lzw_compress() (IS)
* X: cs == NULL
* 1: ready
*
* ExCLisp: {{0 [ cs (AS/.\IS) cs_ready ] 1}}
*/
static ee_lzw_gate_t
lzw_compress_init(ee_lzw_cs_t *cs)
{
if (!cs)
return lzw__gate(EE_GATE_X, EE_LZW_R_NULL);
memset(cs->dict, 0xFF, sizeof(cs->dict));
cs->dict_size = EE_LZW_ALPHA_SZ;
cs->code_count = 0u;
return lzw__ok();
}
/*
* ==================================================================
* LOGIC / COMPRESS
* ==================================================================
*/
/*
* lzw_compress
*
* FRONT: cs initialised; input non-NULL; len > 0 (AS)
* LEAD: IFP pipeline over input bytes (Pivot):
* DISSOLVE seed current_code = input[0]
* DISCOVER I1 lookup dict[cur].next[byte] per byte
* REMAP hit -> extend cur; miss -> emit + add entry + reset
* REMOVE dict-full: emit without adding (gate-0, continue)
* REINDEX emit final code after loop
* REAR: cs->codes[0..code_count-1] = compressed output (IS)
* Z: len == 0
* X: cs or input NULL; code output overflow
* 0: dict reached EE_LZW_DICT_MAX (entries stopped, codes continue)
* 1: compression complete
*
* ExCLisp: {{0 [ (cs,input,len) (AS/.\IS) cs.codes ] 1}}
*/
[[nodiscard]]
static ee_lzw_gate_t
lzw_compress(ee_lzw_cs_t *cs, const uint8_t *input, size_t len)
{
ee_lzw_gate_t result;
uint16_t cur;
size_t i;
if (!cs || !input)
return lzw__gate(EE_GATE_X, EE_LZW_R_NULL);
if (!len)
return lzw__gate(EE_GATE_Z, EE_LZW_R_EMPTY);
result = lzw__ok();
cur = input[0];
for (i = 1u; i < len; i++) {
uint8_t byte = input[i];
uint16_t next = cs->dict[cur].next[byte]; /* I1: O(1) */
if (__builtin_expect(next != EE_LZW_EMPTY, 1)) {
cur = next;
continue;
}
if (__builtin_expect(cs->code_count >= EE_LZW_CODES_MAX, 0))
return lzw__gate(EE_GATE_X, EE_LZW_R_CODES_OVF);
cs->codes[cs->code_count++] = cur;
if (__builtin_expect(cs->dict_size < EE_LZW_DICT_MAX, 1)) {
cs->dict[cur].next[byte] = (uint16_t)cs->dict_size;
cs->dict_size++;
} else {
result = lzw__gate(EE_GATE_0, EE_LZW_R_DICT_FULL);
}
cur = byte;
}
if (__builtin_expect(cs->code_count >= EE_LZW_CODES_MAX, 0))
return lzw__gate(EE_GATE_X, EE_LZW_R_CODES_OVF);
cs->codes[cs->code_count++] = cur;
return result;
}
/*
* ==================================================================
* LOGIC / DECOMPRESS INIT
* ==================================================================
*/
/*
* lzw_decompress_init
*
* FRONT: uninitialised ds (AS)
* LEAD: populate str[0..255] with single-byte literals;
* dict_size = 256; out_len = 0 (Pivot)
* REAR: ds ready for lzw_decompress() (IS)
* X: ds == NULL
* 1: ready
*
* ExCLisp: {{0 [ ds (AS/.\IS) ds_ready ] 1}}
*/
static ee_lzw_gate_t
lzw_decompress_init(ee_lzw_ds_t *ds)
{
uint32_t i;
if (!ds)
return lzw__gate(EE_GATE_X, EE_LZW_R_NULL);
for (i = 0u; i < EE_LZW_ALPHA_SZ; i++) {
ds->str[i].data[0] = (uint8_t)i;
ds->str[i].len = 1u;
}
ds->dict_size = EE_LZW_ALPHA_SZ;
ds->out_len = 0u;
return lzw__ok();
}
/*
* ==================================================================
* LOGIC / DECOMPRESS
* ==================================================================
*/
/*
* lzw_decompress
*
* FRONT: ds initialised; codes non-NULL; count > 0 (AS)
* LEAD: IFP pipeline -- invert I2 (Pivot):
* DISSOLVE output first code's string
* DISCOVER per code: lookup or special-case if code == dict_size
* REMAP known -> copy string; unknown == dict_size -> construct
* REMOVE code > dict_size -> gate-X at structural cause
* REINDEX add new entry = old_string + first_char(cur_string)
* REAR: ds->output[0..out_len-1] = decompressed bytes (IS)
* Z: count == 0
* X: ds or codes NULL; output overflow; string overflow; bad code
* 0: dict full (entries stopped, decompression continues)
* 1: success
*
* ExCLisp: {{0 [ (ds,codes,count) (AS/.\IS) ds.output ] 1}}
*/
[[nodiscard]]
static ee_lzw_gate_t
lzw_decompress(ee_lzw_ds_t *ds, const uint16_t *codes, size_t count)
{
ee_lzw_gate_t result;
uint16_t old;
size_t i;
if (!ds || !codes)
return lzw__gate(EE_GATE_X, EE_LZW_R_NULL);
if (!count)
return lzw__gate(EE_GATE_Z, EE_LZW_R_EMPTY);
result = lzw__ok();
old = codes[0];
if (__builtin_expect(old >= ds->dict_size, 0))
return lzw__gate(EE_GATE_X, EE_LZW_R_BAD_CODE);
{
uint16_t flen = ds->str[old].len;
if (ds->out_len + flen > EE_LZW_OUTPUT_MAX)
return lzw__gate(EE_GATE_X, EE_LZW_R_OUTPUT_OVF);
memcpy(ds->output + ds->out_len, ds->str[old].data, flen);
ds->out_len += flen;
}
for (i = 1u; i < count; i++) {
uint16_t code = codes[i];
const uint8_t *cur_str;
uint16_t cur_len;
/* gate-X at structural cause: code structurally impossible */
if (__builtin_expect(code > ds->dict_size, 0))
return lzw__gate(EE_GATE_X, EE_LZW_R_BAD_CODE);
if (code < ds->dict_size) {
cur_str = ds->str[code].data;
cur_len = ds->str[code].len;
} else {
/* special case: code == dict_size
* string = old_string + old_string[0] */
ee_lzw_str_t *ns = &ds->str[ds->dict_size];
uint16_t olen = ds->str[old].len;
if (__builtin_expect((uint32_t)olen + 1u > EE_LZW_STR_MAX, 0))
return lzw__gate(EE_GATE_X, EE_LZW_R_STR_OVF);
memcpy(ns->data, ds->str[old].data, olen);
ns->data[olen] = ds->str[old].data[0];
ns->len = (uint16_t)(olen + 1u);
cur_str = ns->data;
cur_len = ns->len;
}
if (__builtin_expect(ds->out_len + cur_len > EE_LZW_OUTPUT_MAX, 0))
return lzw__gate(EE_GATE_X, EE_LZW_R_OUTPUT_OVF);
memcpy(ds->output + ds->out_len, cur_str, cur_len);
ds->out_len += cur_len;
/* add new entry: old_string + first_char(cur_string) */
if (__builtin_expect(ds->dict_size < EE_LZW_DICT_MAX, 1)) {
ee_lzw_str_t *ne = &ds->str[ds->dict_size];
uint16_t olen = ds->str[old].len;
if ((uint32_t)olen + 1u <= EE_LZW_STR_MAX) {
memcpy(ne->data, ds->str[old].data, olen);
ne->data[olen] = cur_str[0];
ne->len = (uint16_t)(olen + 1u);
ds->dict_size++;
}
} else {
result = lzw__gate(EE_GATE_0, EE_LZW_R_DICT_FULL);
}
old = code;
}
return result;
}
/*
* ==================================================================
* LOGIC / TIMING (integer nanoseconds -- no IEEE 754)
* ==================================================================
*/
static uint64_t
lzw_now_ns(void)
{
struct timespec ts;
if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0)
return 0u;
return (uint64_t)ts.tv_sec * UINT64_C(1000000000)
+ (uint64_t)ts.tv_nsec;
}
/*
* ==================================================================
* LOGIC / SELF-TEST (ppo-2: SELF-TESTS AT STARTUP)
* ==================================================================
*/
/* file-scope to avoid 2MB+ stack allocation */
static ee_lzw_cs_t g_self_cs;
static ee_lzw_ds_t g_self_ds;
/*
* lzw_self_test
*
* FRONT: no external state (AS)
* LEAD: nine checks against hand-derivable values (Pivot)
* REAR: gate-1 all pass; gate-0 + stderr on failure (IS)
* 0: any check failed
* 1: all nine passed
*
* Checks:
* 1. sizeof(ee_lzw_gate_t) == 4
* 2. sizeof(ee_lzw_entry_t) == 512
* 3. EE_LZW_EMPTY == 0xFFFF
* 4. EE_LZW_EMPTY > EE_LZW_DICT_MAX - 1 (sentinel valid)
* 5. compress("A") -> codes = {65}
* 6. compress("AB") -> codes = {65, 66}
* 7. after compress("AB"): dict['A']['B'] == 256 (I1 spot-check)
* 8. round-trip "TOBEORNOT" correct length
* 9. round-trip "TOBEORNOT" correct content
*
* ExCLisp: {{0 [ void (AS/.\IS) gate_1_or_0 ] 1}}
*/
[[nodiscard]]
static ee_lzw_gate_t
lzw_self_test(void)
{
#define LZW_ST(expr, msg) \
do { \
if (!(expr)) { \
fprintf(stderr, \
"[lzw_self_test] FAIL: %s\n", \
(msg)); \
return lzw__gate(EE_GATE_0, \
EE_LZW_R_SELF_FAIL); \
} \
} while (0)
/* 1-4: structural */
LZW_ST(sizeof(ee_lzw_gate_t) == 4u, "sizeof gate == 4");
LZW_ST(sizeof(ee_lzw_entry_t) == 512u, "sizeof entry == 512");
LZW_ST(EE_LZW_EMPTY == 0xFFFFu, "sentinel == 0xFFFF");
LZW_ST(EE_LZW_EMPTY > EE_LZW_DICT_MAX - 1u,
"sentinel > max valid code");
/* 5: compress("A") -> {65} */
lzw_compress_init(&g_self_cs);
{
ee_lzw_gate_t g_ = lzw_compress(&g_self_cs,
(const uint8_t *)"A", 1u);
LZW_ST(g_.state == EE_GATE_1, "compress A gate");
}
LZW_ST(g_self_cs.code_count == 1u, "compress A: one code");
LZW_ST(g_self_cs.codes[0] == 65u, "compress A: code == 65");
/* 6: compress("AB") -> {65, 66} */
lzw_compress_init(&g_self_cs);
{
ee_lzw_gate_t g_ = lzw_compress(&g_self_cs,
(const uint8_t *)"AB", 2u);
LZW_ST(g_.state == EE_GATE_1, "compress AB gate");
}
LZW_ST(g_self_cs.code_count == 2u, "compress AB: two codes");
LZW_ST(g_self_cs.codes[0] == 65u, "compress AB: code[0] == 65");
LZW_ST(g_self_cs.codes[1] == 66u, "compress AB: code[1] == 66");
/* 7: I1 spot-check: dict['A']['B'] == 256 after "AB" */
LZW_ST(g_self_cs.dict[65].next[66] == 256u,
"dict['A']['B'] == 256 after AB");
/* 8-9: round-trip "TOBEORNOT" */
lzw_compress_init(&g_self_cs);
{
ee_lzw_gate_t g_ = lzw_compress(&g_self_cs,
(const uint8_t *)"TOBEORNOT", 9u);
LZW_ST(g_.state == EE_GATE_1, "compress TOBEORNOT gate");
}
lzw_decompress_init(&g_self_ds);
{
ee_lzw_gate_t g_ = lzw_decompress(&g_self_ds,
g_self_cs.codes, g_self_cs.code_count);
LZW_ST(g_.state == EE_GATE_1, "decompress TOBEORNOT gate");
}
g_self_ds.output[g_self_ds.out_len] = '\0';
LZW_ST(g_self_ds.out_len == 9u, "round-trip TOBEORNOT: len");
LZW_ST(memcmp(g_self_ds.output,
(const uint8_t *)"TOBEORNOT", 9u) == 0,
"round-trip TOBEORNOT: content");
#undef LZW_ST
return lzw__ok();
}
/*
* ==================================================================
* LOGIC / TEST SUITE
* ==================================================================
*/
typedef struct lzw_test {
const char *name;
const char *input;
} lzw_test_t;
static const lzw_test_t lzw_tests[] = {
{ "TOBEORNOTTOBEORTOBEORNOT",
"TOBEORNOTTOBEORTOBEORNOT" },
{ "ABABABA",
"ABABABA" },
{ "single char A",
"A" },
{ "two chars AB",
"AB" },
{ "ABCABCABC",
"ABCABCABC" },
{ "fox sentence",
"THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG." },
{ "digits 12312312312345",
"12312312312345" },
{ "Hello World round-trip",
"Hello, World! Hello, Programming!" },
};
static const size_t lzw_test_count =
sizeof(lzw_tests) / sizeof(lzw_tests[0]);
/* file-scope to avoid 2MB+ stack allocation in test runner */
static ee_lzw_cs_t g_test_cs;
static ee_lzw_ds_t g_test_ds;
/*
* lzw_run_test
*
* FRONT: test with name and input string (AS)
* LEAD: compress then decompress; compare to input (Pivot)
* REAR: printed result line; true if round-trip correct (IS)
* 1: round-trip correct
* 0: mismatch or gate-X (false returned)
*
* ExCLisp: {{0 [ test (AS/.\IS) bool ] 1}}
*/
static bool
lzw_run_test(const lzw_test_t *test)
{
size_t ilen = strlen(test->input);
lzw_compress_init(&g_test_cs);
ee_lzw_gate_t cg = lzw_compress(&g_test_cs,
(const uint8_t *)test->input, ilen);
if (cg.state == EE_GATE_X) {
printf(" FAIL [%s]: compress gate-X 0x%04x\n",
test->name, cg.reason);
return false;
}
lzw_decompress_init(&g_test_ds);
ee_lzw_gate_t dg = lzw_decompress(&g_test_ds,
g_test_cs.codes, g_test_cs.code_count);
if (dg.state == EE_GATE_X) {
printf(" FAIL [%s]: decompress gate-X 0x%04x\n",
test->name, dg.reason);
return false;
}
g_test_ds.output[g_test_ds.out_len] = '\0';
if (g_test_ds.out_len != ilen ||
memcmp(g_test_ds.output, test->input, ilen) != 0) {
printf(" FAIL [%s]: round-trip mismatch\n", test->name);
return false;
}
printf(" PASS [%s]: %zu -> %u codes -> %u bytes\n",
test->name,
ilen,
g_test_cs.code_count,
g_test_ds.out_len);
return true;
}
/*
* ==================================================================
* LOGIC / INTERACTIVE MODE
* ==================================================================
*/
/* file-scope to avoid 2MB+ stack allocation in interactive */
static ee_lzw_cs_t g_int_cs;
static ee_lzw_ds_t g_int_ds;
/*
* lzw_interactive
*
* FRONT: stdin open (AS)
* LEAD: read lines; ==comp / ==decomp switch mode;
* compress or decompress input (Pivot)
* REAR: interactive session runs until EOF (IS)
* 1: always (session complete on EOF)
*
* ExCLisp: {{0 [ void (AS/.\IS) void ] 1}}
*/
static void
lzw_interactive(void)
{
char line[EE_LZW_CODES_MAX];
uint8_t mode = 0u; /* 0=none 1=compress 2=decompress */
printf("LZW Interactive Mode\n");
printf("Commands: ==comp, ==decomp, or type text\n");
printf("Ctrl+C to exit\n\n");
while (fgets(line, (int)sizeof(line), stdin)) {
line[strcspn(line, "\n")] = '\0';
if (strncmp(line, "==comp", 6) == 0) {
mode = 1u;
printf("Compression mode\n");
continue;
}
if (strncmp(line, "==decomp", 8) == 0) {
mode = 2u;
printf("Decompression mode\n");
continue;
}
if (mode == 1u) {
lzw_compress_init(&g_int_cs);
uint64_t t0 = lzw_now_ns();
ee_lzw_gate_t g = lzw_compress(&g_int_cs,
(const uint8_t *)line, strlen(line));
uint64_t ns = lzw_now_ns() - t0;
if (g.state == EE_GATE_X) {
printf("gate-X: 0x%04x\n", g.reason);
continue;
}
for (uint32_t i = 0u; i < g_int_cs.code_count; i++) {
printf("%u", g_int_cs.codes[i]);
if (i < g_int_cs.code_count - 1u)
putchar(',');
}
putchar('\n');
printf("// %zu chars -> %u codes %" PRIu64 " ns\n",
strlen(line), g_int_cs.code_count, ns);
} else if (mode == 2u) {
uint16_t codes[EE_LZW_CODES_MAX];
uint32_t count = 0u;
char *tok = strtok(line, ",");
while (tok && count < EE_LZW_CODES_MAX) {
codes[count++] = (uint16_t)atoi(tok);
tok = strtok(NULL, ",");
}
lzw_decompress_init(&g_int_ds);
uint64_t t0 = lzw_now_ns();
ee_lzw_gate_t g = lzw_decompress(&g_int_ds,
codes, count);
uint64_t ns = lzw_now_ns() - t0;
if (g.state == EE_GATE_X) {
printf("gate-X: 0x%04x\n", g.reason);
continue;
}
g_int_ds.output[g_int_ds.out_len] = '\0';
printf("%s\n", g_int_ds.output);
printf("// %u codes -> %u bytes %" PRIu64 " ns\n",
count, g_int_ds.out_len, ns);
}
}
}
/*
* ==================================================================
* LOGIC / MAIN
* ==================================================================
*/
int
main(int argc, char **argv)
{
printf("LZW -- ppo-2 C23 v2.1.0\n\n");
/* ppo-2: self-tests fire before any external interaction */
printf("[SELF-TEST] LZW (9 checks)... ");
fflush(stdout);
ee_lzw_gate_t st = lzw_self_test();
if (st.state != EE_GATE_1) {
fprintf(stderr, "FAIL (0x%04x)\n", st.reason);
return 1;
}
printf("PASS\n\n");
if (argc > 1 && strcmp(argv[1], "test") == 0) {
printf("Test suite (%zu cases):\n\n", lzw_test_count);
uint64_t t0 = lzw_now_ns();
int passed = 0;
for (size_t i = 0u; i < lzw_test_count; i++)
if (lzw_run_test(&lzw_tests[i]))
passed++;
uint64_t elapsed = lzw_now_ns() - t0;
printf("\nResults: %d/%zu passed"
" %" PRIu64 " ns gate-1 = ALLOW\n",
passed, lzw_test_count, elapsed);
return passed == (int)lzw_test_count ? 0 : 1;
}
lzw_interactive();
return 0;
}
@opsec-ee
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opsec-ee commented Mar 20, 2026

$ ./lzw test

LZW -- ppo-2 C23 v2.1.0

[SELF-TEST] LZW (9 checks)... PASS

Test suite (8 cases):

PASS [TOBEORNOTTOBEORTOBEORNOT]: 24 -> 16 codes -> 24 bytes
PASS [ABABABA]: 7 -> 4 codes -> 7 bytes
PASS [single char A]: 1 -> 1 codes -> 1 bytes
PASS [two chars AB]: 2 -> 2 codes -> 2 bytes
PASS [ABCABCABC]: 9 -> 6 codes -> 9 bytes
PASS [fox sentence]: 44 -> 42 codes -> 44 bytes
PASS [digits 12312312312345]: 14 -> 9 codes -> 14 bytes
PASS [Hello World round-trip]: 33 -> 30 codes -> 33 bytes

Results: 8/8 passed 2915980 ns gate-1 = ALLOW

Linux. Zero warnings. 8/8. 2.9ms for all eight cases. Clean.

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