59120c330
Ron Yorston
2021-02-02
Subject
libbb: code shrink and speed up find_applet_by_name()
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libbb/appletlib.c+17 -79
| @@ -176,7 +176,7 @@ void FAST_FUNC bb_show_usage(void) | |
| int FAST_FUNC find_applet_by_name(const char *name) | |
| { | |
| - | unsigned i, max; |
| + | unsigned i; |
| int j; | |
| const char *p; | |
| @@ -200,105 +200,43 @@ int FAST_FUNC find_applet_by_name(const char *name) | |
| #endif | |
| p = applet_names; | |
| - | i = 0; |
| #if KNOWN_APPNAME_OFFSETS <= 0 | |
| - | max = NUM_APPLETS; |
| + | i = 0; |
| #else | |
| - | max = NUM_APPLETS * KNOWN_APPNAME_OFFSETS; |
| + | i = NUM_APPLETS * (KNOWN_APPNAME_OFFSETS - 1); |
| for (j = ARRAY_SIZE(applet_nameofs)-1; j >= 0; j--) { | |
| const char *pp = applet_names + applet_nameofs[j]; | |
| if (strcmp(name, pp) >= 0) { | |
| //bb_error_msg("name:'%s' >= pp:'%s'", name, pp); | |
| p = pp; | |
| - | i = max - NUM_APPLETS; |
| break; | |
| } | |
| - | max -= NUM_APPLETS; |
| + | i -= NUM_APPLETS; |
| } | |
| - | max /= (unsigned)KNOWN_APPNAME_OFFSETS; |
| i /= (unsigned)KNOWN_APPNAME_OFFSETS; | |
| - | //bb_error_msg("name:'%s' starting from:'%s' i:%u max:%u", name, p, i, max); |
| + | //bb_error_msg("name:'%s' starting from:'%s' i:%u", name, p, i); |
| #endif | |
| /* Open-coded linear search without strcmp/strlen calls for speed */ | |
| - | |
| - | #if 0 /*BB_UNALIGNED_MEMACCESS_OK && BB_LITTLE_ENDIAN*/ |
| - | /* skip "[\0" name, it's surely not it */ |
| - | if (ENABLE_TEST && LONE_CHAR(p, '[')) |
| - | i++, p += 2; |
| - | /* All remaining applet names in p[] are at least 2 chars long */ |
| - | /* name[] is also at least 2 chars long */ |
| - | |
| - | n32 = (name[0] << 0) | (name[1] << 8) | (name[2] << 16); |
| - | while (i < max) { |
| - | uint32_t p32; |
| - | char ch; |
| - | |
| - | /* Quickly check match of the first 3 bytes */ |
| - | move_from_unaligned32(p32, p); |
| - | p += 3; |
| - | if ((p32 & 0x00ffffff) != n32) { |
| - | /* Most likely case: 3 first bytes do not match */ |
| - | i++; |
| - | if ((p32 & 0x00ff0000) == '\0') |
| - | continue; // p[2] was NUL |
| - | p++; |
| - | if ((p32 & 0xff000000) == '\0') |
| - | continue; // p[3] was NUL |
| - | /* p[0..3] aren't matching and none is NUL, check the rest */ |
| - | while (*p++ != '\0') |
| - | continue; |
| - | continue; |
| - | } |
| - | |
| - | /* Unlikely branch: first 3 bytes ([0..2]) match */ |
| - | if ((p32 & 0x00ff0000) == '\0') { |
| - | /* name is 2-byte long, it is full match */ |
| - | //bb_error_msg("found:'%s' i:%u", name, i); |
| - | return i; |
| - | } |
| - | /* Check remaining bytes [3..NUL] */ |
| - | ch = (p32 >> 24); |
| - | j = 3; |
| - | while (ch == name[j]) { |
| - | if (ch == '\0') { |
| - | //bb_error_msg("found:'%s' i:%u", name, i); |
| - | return i; |
| - | } |
| - | ch = *++p; |
| - | j++; |
| - | } |
| - | /* Not a match. Skip it, including NUL */ |
| - | while (ch != '\0') |
| - | ch = *++p; |
| - | p++; |
| - | i++; |
| - | } |
| - | return -1; |
| - | #else |
| - | while (i < max) { |
| - | char ch; |
| - | j = 0; |
| - | /* Do we see "name\0" in applet_names[p] position? */ |
| - | while ((ch = *p) == name[j]) { |
| - | if (ch == '\0') { |
| + | while (*p) { |
| + | /* Do we see "name\0" at current position in applet_names? */ |
| + | for (j = 0; *p == name[j]; ++j) { |
| + | if (*p++ == '\0') { |
| //bb_error_msg("found:'%s' i:%u", name, i); | |
| return i; /* yes */ | |
| } | |
| - | p++; |
| - | j++; |
| } | |
| - | /* No. |
| - | * p => 1st non-matching char in applet_names[], |
| - | * skip to and including NUL. |
| - | */ |
| - | while (ch != '\0') |
| - | ch = *++p; |
| - | p++; |
| + | /* No. Have we gone too far, alphabetically? */ |
| + | if (*p > name[j]) { |
| + | //bb_error_msg("break:'%s' i:%u", name, i); |
| + | break; |
| + | } |
| + | /* No. Move to the start of the next applet name. */ |
| + | while (*p++ != '\0') |
| + | continue; |
| i++; | |
| } | |
| return -1; | |
| - | #endif |
| } | |