printf - C++ Reference

Hash Table for Embedded Systems?

Hi all,
I have a CSV file of about 1500 elements that maps a long integer (uint32_t) to a 128-char ASCII binary string. When I want to access one of these strings, I use a fairly simple lookup strategy that returns this bitstring in a char array, which I then convert to a series of hex values for storage in a struct.
This is incredibly inefficient, and does too much disk access. Ideally, I'd want to have a hash table implementation with all normal functions, plus an option to reload from a predefined location on disk, with the added constraint that it be optimized for an embedded system (64kiB RAM allotted, 1GHz CPU; though this is a really low priority task e.g. Maximum NICE level).
Here's a partial C implementation of the current lookup method that compiles under -Werror, -Wall, -Wpedantic:
// reading a text file #include  #include  #include  #include  #include  #include  #define MAX_LINE_LENGTH 100 #define NUM_BITS_PER_CMD 96 //give 2 pointers and mode as input void print_bitstring(char *p) { for (int i = 0; i < strlen(p); i++) { if(i % 4 == 0 && i) printf(" "); if(i % 8 == 0 && i) printf("\n"); printf("%c", p[i]); } } void expander(uint32_t mode, char *f_b, char *s_b) { memset((unsigned char *)f_b, 0, strlen(f_b)); memset((unsigned char *)s_b, 0, strlen(f_b)); char temp1[MAX_LINE_LENGTH], temp2[2*MAX_LINE_LENGTH]; // Converting incoming mode to a string // reference: https://stackoverflow.com/questions/2709713/how-to-convert-unsigned-long-to-string // u32_t format specifier found here: https://stackoverflow.com/questions/3168275/printf-format-specifiers-for-uint32-t-and-size-t const int n = snprintf(NULL, 0, "%"PRIu32"", mode); assert(n > 0); char input[n+1]; int c = snprintf(input, n+1, "%"PRIu32"", mode); assert(input[n] == '\0'); assert(c == n); char command[MAX_LINE_LENGTH], mode_id[MAX_LINE_LENGTH], *pt, *line = NULL; FILE *fp; size_t len = 0; ssize_t read; fp = fopen("./lookupTable.csv", "r"); if (fp != NULL) { // Reading in lookup table line by line // reference: https://stackoverflow.com/questions/3501338/c-read-file-line-by-line while ( (read = getline (&line, &len, fp)) != -1 ) { line[read - 1] = '\0'; char delimiter[] = ","; //size_t pos = 0; //mode_id = ""; // Read tokens from CSV file // reference: http://www.cplusplus.com/reference/cstring/strtok/ pt = strtok(line, delimiter); if (pt != NULL) { // Filling mode_id // reference: http://man7.org/linux/man-pages/man3/strcpy.3.html // I considered strlcpy, but strdup should work fine for our purposes. // mode_id = strdup(pt); strncpy(mode_id, pt, sizeof(mode_id)); #if(DEBUG) //printf("mode_id is %d bytes long.\n", strlen(mode_id)); #endif assert(mode_id != NULL); // strlcpy(mode_id, pt, MAX_LINE_LENGTH); pt = strtok(NULL, delimiter); } else { #if(DEBUG) printf("No comma found when parsing CSV! Exiting...\n"); #endif exit(EXIT_FAILURE); } if (pt != NULL) { strncpy(command, pt, sizeof(command)); //command = strdup(pt); assert(command != NULL); } else { #if(DEBUG) printf("No comma found when parsing CSV! Exiting...\n"); #endif exit(EXIT_FAILURE); } if(strcmp(input, mode_id) == 0) { #if(DEBUG) printf("Found a matching mode_id!\n"); #endif if(strlen(command) == NUM_BITS_PER_CMD) { strncpy(temp1, command, NUM_BITS_PER_CMD + 1); #if(DEBUG) printf("Copying command into f_b and s_b...\n"); #endif for(int i = 0; i < strlen(temp1); i++) { f_b[i]=temp1[i]; s_b[i]=temp1[i]; } } else { printf("Command was longer than %d bits. Detected length: %zu\n", NUM_BITS_PER_CMD, strlen(command)); printf("Command string:\n"); print_bitstring(command); strncpy(temp2, command, NUM_BITS_PER_CMD + 1); int j = 0; for(int i = 0; i < strlen(temp2); i++) { #if(DEBUG) if(i == 0) printf("Copying first %d bits into f_b\n", NUM_BITS_PER_CMD); if(i == NUM_BITS_PER_CMD) printf("Copying remaining %zu bits into s_b\n", strlen(temp2)-NUM_BITS_PER_CMD); #endif if(i < NUM_BITS_PER_CMD) { // Straightforward copy, maybe could just use strncpy? f_b[i]=temp2[i]; } else { // Overflows excess command bits into s_b s_b[j]=temp2[i]; j++; } } #if(DEBUG) if(j > 0) printf("Buffer contained %d extra bytes, copied into s_b\n", j); #endif } } } fclose(fp); } else { #if(DEBUG) printf("Unable to open file\n"); #endif exit(EXIT_FAILURE); } } int main (void) { uint32_t mode=1118074860;//32 bit mode ID // Corresponding shell command: grep 1118 lookupTable.csv | sed 's/.*,//' | sed -e "s/.\{8\}/&\n/g" char f_b[NUM_BITS_PER_CMD + 1], s_b[NUM_BITS_PER_CMD + 1]; //constant buffers to LIIB f_b[NUM_BITS_PER_CMD] = '\0'; s_b[NUM_BITS_PER_CMD] = '\0'; expander(mode, f_b, s_b); printf("Looping over first word (length: %zu)...\n", strlen(f_b)); print_bitstring(f_b); printf("\n"); printf("Looping over second word (length: %zu)...\n", strlen(s_b)); print_bitstring(s_b); return 0; } 
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How do I convert a binary string like "010011101" to an int, and how do I convert an int, like 5, to a string "101" in C? Writes the C string pointed by format to the standard output ().If format includes format specifiers (subsequences beginning with %), the additional arguments following format are formatted and inserted in the resulting string replacing their respective specifiers. Parameters format C string that contains the text to be written to stdout. It can optionally contain embedded format specifiers ... By default, C provides a great deal of power for formatting output. The standard display function, printf, takes a "format string" that allows you to specify lots of information about how a program is formatted. Note: if you are looking for information on formatting output in C++, take a look at formatting C++ output using iomanip. Let's look at the anatomy of a format string followed by some ... @EvilTeach: You're using a ternary operator yourself as a parameter to strcat()!I agree that strcat is probably easier to understand than post-incrementing a dereferenced pointer for the assignment, but even beginners need to know how to properly use the standard library. Maybe using an indexed array for assignment would have been a good demonstration (and will actually work, since b isn't ... Free online string to binary converter. Just load your string and it will automatically get converted to a binary string. There are no ads, popups or nonsense, just a string to binary converter. Load a string, get its binary representation. Created for developers by developers from team Browserling. @mVChr: str.format() is the wrong tool anyway, you would use format(i, 'b') instead. Take into account that that also gives you padding and alignment options though; format(i, '016b') to format to a 16-bit zero-padded binary number. To do the same with bin() you'd have to add a str.zfill() call: bin(i)[2:].zfill(16) (no need to call str()!).format()'s readability and flexibility (dynamic ... PyFormat Using % and .format() for great good! Python has had awesome string formatters for many years but the documentation on them is far too theoretic and technical. With this site we try to show you the most common use-cases covered by the old and new style string formatting API with practical examples. In this C programming language tutorial we take another look at the printf function. We will look at how to use format specifiers to print formatted output onto the screen. The topics covered are; a little printf background, format specifiers and conversions, formatting of different types and format conversions of strings. printf Background The precision is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted. Sr.No. Length & Description; 1: h. The argument is interpreted as a short int or unsigned short int (only applies to integer specifiers: i, d, o, u, x and X). 2: l. The argument is interpreted as a long int or unsigned long int for integer specifiers ... Format specifier in C language. List: Integer format specifier %d, Float format specifier %f, character format specifier %c, string format specifier %s. Format specifiers define the type of data. C provide different types of format specifier for each data types. short, long, character signed, unsigned format specifier.

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C Program To Convert Decimal To Binary Number using ...

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