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feat: cdma

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eneller
2026-03-23 21:22:38 +01:00
parent 37cd47f56a
commit e51446df9f
2 changed files with 27 additions and 11 deletions
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30
cdma.Rmd
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@@ -27,12 +27,21 @@ ASCII characters require 7 bits of information per character.
```{r input} ```{r input}
lines <- readLines('./input.txt',encoding = 'ASCII') lines <- readLines('./input.txt',encoding = 'ASCII')
strToBin <- function(s){ strToBin <- function(s){
# FIXME for strings longer than 1
r <- as.integer(intToBits(utf8ToInt(s))) r <- as.integer(intToBits(utf8ToInt(s)))
r <- r[1:7] r <- r[1:7]
return(r) return(r)
} }
lines_bin <- do.call(rbind, lapply(lines, strToBin))
lines_bin <- list()
for (line in lines){
line_bin <- list()
for (char in strsplit(line, "")[[1]]){
s <- strToBin(char)
line_bin <- append(line_bin, s)
}
lines_bin <- append(lines_bin, list(line_bin))
}
lines_bin <- do.call(rbind,lines_bin)
``` ```
```{r input-demo, echo=FALSE} ```{r input-demo, echo=FALSE}
@@ -63,7 +72,7 @@ for (j in 1:ncol(lines_bin)){
col <- lines_bin[,j] col <- lines_bin[,j]
output_symbol <- 0 output_symbol <- 0
for (i in 1:length(col)){ for (i in 1:length(col)){
symbol <- col[i] # the symbol to be encoded symbol <- col[[i]] # the symbol to be encoded
code <- orthogonals[i,] # the code vector code <- orthogonals[i,] # the code vector
single_symbol <- (-1)^(1+symbol) * code # the resulting encoded vector single_symbol <- (-1)^(1+symbol) * code # the resulting encoded vector
@@ -97,19 +106,26 @@ decoded_m == lines_bin
Then we apply our text encoding on each line separately, respecting the LSB/MSB order. Then we apply our text encoding on each line separately, respecting the LSB/MSB order.
```{r text-decode} ```{r text-decode}
chunk <- function(x, chunk_size) { chunk <- function(x, chunk_size) {
split(x, cut(seq_along(x), breaks = chunks <- split(x, cut(seq_along(x), breaks =
seq(0, length(x), by = chunk_size), include.lowest = TRUE)) seq(0, length(x), by = chunk_size), include.lowest = TRUE))
lapply(chunks, as.list)
} }
final <- c('','','','')
for (i in 1:nrow(decoded_m)){ for (i in 1:nrow(decoded_m)){
line <- decoded_m[i,] line <- decoded_m[i,]
symbols <- chunk(line, 7) symbols <- chunk(line, 7)
for (symbol in symbols){ for (j in 1:length(symbols)){
binary_str <- paste(rev(symbol), collapse = "") binary_str <- paste(rev(symbols[[j]]), collapse = "")
# Convert the binary string to a decimal value # Convert the binary string to a decimal value
decimal <- strtoi(binary_str, base = 2) decimal <- strtoi(binary_str, base = 2)
# Convert the decimal value to an ASCII character # Convert the decimal value to an ASCII character
char <- intToUtf8(decimal) char <- intToUtf8(decimal)
print(char) final[i] <- paste0(final[i], char)
} }
} }
```
```{r text-decode-demo, echo=FALSE}
print(final)
``` ```

8
input.txt
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@@ -1,4 +1,4 @@
a da
b cb
c bc
d ad