hoo2/micro_assign_1
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FIX: Check for corner cases added

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This commit is contained in:
Christos Choutouridis 2020-05-03 14:54:29 +01:00
parent caa10a9349
commit 849b826457
1 changed files with 16 additions and 5 deletions
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21
main.c
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@ -28,14 +28,17 @@
/*! /*!
* String length calculation. * String length calculation.
* @arg R0: Pointer to string * @arg src{R0} Pointer to string
* @return R0: String length (unsigned) * @return {R0} String length, -1 if src is NULL
*/ */
__asm uint32_t strLength (const char* src) { __asm uint32_t strLength (const char* src) {
// R0: length, return value // R0: length, return value
// R1: src // R1: src
// R2: v = *src // R2: v = *src
MOV R1, R0 // Get variable MOV R1, R0 // Get variable
CMP R1, #0 // if (src{R1} == NULL)
MOVEQ R0, #-1 // return -1;
BXEQ LR
MOV R0, #0 // length{R0} =0; MOV R0, #0 // length{R0} =0;
len_loop // do { len_loop // do {
LDRB R2, [R1], #1 // v{R2} = *src++; LDRB R2, [R1], #1 // v{R2} = *src++;
@ -62,6 +65,8 @@ __asm uint32_t isPalindrome (const char* src) {
// R3: v1 = src[i] // R3: v1 = src[i]
// R4: v2 = src[j] // R4: v2 = src[j]
PUSH {R4, LR} PUSH {R4, LR}
CMP R0, #0 // if (src{R0} == NULL)
BEQ pal_false // return false;
MOV R4, R0 // save R0 MOV R4, R0 // save R0
BL strLength // j{R2} = strLength(src) - 1 BL strLength // j{R2} = strLength(src) - 1
SUB R2, R0, #1 SUB R2, R0, #1
@ -77,7 +82,7 @@ pal_loop
ADDEQ R1, R1, #1 // ++i; ADDEQ R1, R1, #1 // ++i;
SUBEQ R2, R2, #1 // --j; SUBEQ R2, R2, #1 // --j;
BEQ pal_loop // // goto loop; BEQ pal_loop // // goto loop;
// } else pal_false // } else
MOV R0, #0 // return *RESULT = 0; MOV R0, #0 // return *RESULT = 0;
LDR R1, =RESULT LDR R1, =RESULT
STRB R0, [R1] STRB R0, [R1]
@ -91,14 +96,20 @@ pal_true
} }
/*! /*!
* Main routine * Main routine.
* @note
* This routine plays the role of debuging-mode unit testing.
*/ */
int main(void) { int main(void) {
const char *s1 = "hello world!"; // Not a palindrome const char *s1 = "hello world!"; // Not a palindrome
const char *s2 = "aibohphobia"; // Aibophobia def= "Fear of palindromes", palindrome. const char *s2 = "aibohphobia"; // Aibophobia def= "Irational fear of palindromes", palindrome.
const char *s3 = ""; // Empty string, palindrome.
const char *s4 = 0; // NULL pointer. Out of scope, not palindrome
uint32_t res1 = isPalindrome (s1); // Test case 1 uint32_t res1 = isPalindrome (s1); // Test case 1
uint32_t res2 = isPalindrome (s2); // Test case 2 uint32_t res2 = isPalindrome (s2); // Test case 2
uint32_t res3 = isPalindrome (s3); // Test case 3
uint32_t res4 = isPalindrome (s4); // Test case 4
while (1); // Trap forever while (1); // Trap forever
//return 0; //!< comment out return, to suppress "statement is unreachable" warning. //return 0; //!< comment out return, to suppress "statement is unreachable" warning.